REPORT NUMBER
National River Health Program
2
healthy rivers living rivers
rivers for life
Environmental Water Requirements to Maintain Groundwater Dependent Ecosystems
E N V I R O N M E N TA L F L O W S I N I T I AT I V E T E C H N I C A L R E P O R T
REPORT NUMBER 2
Environmental Water
Requirements to
Maintain Groundwater
Dependent Ecosystems
A Commonwealth Government Initiative
National River Health Program
healthy rivers living rivers
rivers for life
E N V I R O N M E N TA L F L O W S I N I T I AT I V E T E C H N I C A L R E P O R T
REPORT NUMBER 2
Environmental Water
Requirements to
Maintain Groundwater
Dependent Ecosystems
Author: Sinclair Knight Merz Pty Ltd
A Commonwealth Government Initiative
Published By:
Environment Australia
GPO Box 787
CANBERRA ACT 2601
Authors:
Sinclair Knight Merz Pty. Ltd.
PO Box 2500
Malvern VIC 3144
http://www.skm.com.au
Copyright:
 Commonwealth of Australia, November 2001
This work is copyright. Information contained in this publication may be copied
or reproduced for study, research, information, or educational purposes,
subject to inclusion of an acknowledgment of the source. Requests and
inquiries concerning reproduction and rights should be addressed to:
Assistant Secretary
Water Branch
Environment Australia
GPO Box 787
Canberra ACT 2601
Disclaimer:
The views and opinions expressed in this publication are those of the authors
and do not necessarily reflect those of the Commonwealth Government or the
Minister for the Environment and Heritage.
While reasonable efforts have been made to ensure that the contents of this
publication are factually correct, the Commonwealth does not accept
responsibility for the accuracy or completeness of the contents, and shall not
be liable for any loss or damage that may be occasioned directly or indirectly
through the use of, or reliance on, the contents of this publication.
The information contained in this work has been published by Environment
Australia to help develop community, industry and management expertise in
sustainable water resources management and raise awareness of river health
issues and the needs of our rivers. The Commonwealth recommends that
readers exercise their own skill and care with respect to their use of the
material published in this report and that users carefully evaluate the accuracy,
currency, completeness and relevance of the material for their purposes.
Citation:
For bibliographic purposes this report may be cited as:
Sinclair Knight Merz, Environmental Water Requirements of Groundwater
Dependent Ecosystems (2001), Environmental Flows Initiative Technical
Report Number 2, Commonwealth of Australia, Canberra.
ISBN:
0642547696
Information:
For additional information about this publication, please contact the author(s).
Alternatively, you can contact the Community Information Unit of Environment
Australia on toll free 1800 803 772.
Cover Photo credits:
Main image: West Finnis spring ( Western Mining Corporation Ltd.).
Top thumbnail image: Nameless creek in Gulf of Carpenteria region ( PD
Canty).
Middle thumbnail image: Creek sampling ( Commonwealth of Australia).
Bottom thumbnail image: Water reflections in Cathedral Chasm ( PD Canty).
Contents
Executive Summary
iv
1. Introduction
1.1 Introduction
1.2 Study objectives
1.3 Structure of report
1
1
2
3
2. Australian Groundwater Dependent Ecosystems
4
2.1 Ecosystems and groundwater dependency
4
2.2 Australian groundwater dependent ecosystems
6
2.2.1
Terrestrial vegetation 7
2.2.2
Wetlands 8
2.2.3
Estuarine and near shore marine systems 10
2.2.4
River base flow systems 11
2.2.5
Cave and aquifer ecosystems 12
2.2.6
Terrestrial fauna 14
2.3 Threatening processes
14
2.3.1
Water resource development 15
2.3.2
Agricultural land use 16
2.3.3
Acid sulphate soils 18
2.3.4
Urban and commercial development 19
2.3.5
Mining 20
2.3.6
Plantation forestry 22
2.4 Important groundwater dependent ecosystems
23
3. Environmental Water Requirements of Groundwater
Dependent Ecosystems
27
3.1 Introduction
27
3.2 Identifying potentially groundwater dependent
ecosystems
27
3.3 Dependency analysis
30
3.4 Assessment of current or natural water regime
33
3.4.1Determining the processes or uses for which water is
3.4.2
Sources of water exploited by ecosystems 34
3.4.3
Patterns of water usage 35
3.4.3.1Threshold values for groundwater attributes
3.4.3.2
Rates of use 36
3.4.3.3Temporal distribution of groundwater requirement
3.5 Water requirement determination
41
3.6 Determining the environmental water requirement in
resource and information limited environments
44
4. Environmental water provisions for groundwater
dependent ecosystems
47
4.1 Introduction
47
4.2 Environmental flow provisions
48
4.3 Environmental water provisions
50
4.3.1
Groundwater basin definition 51
4.3.2Compilation of existing knowledge and information
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4.3.3
Initial review 53
4.3.4 Environmental water requirement determination 53
4.3.5
Strategic planning 54
4.3.6
Supplementary investigations 55
4.3.7
Management impact assessment 55
4.3.8
Socio-economic impact assessment 55
4.3.9
Establish environmental water provisions 55
4.3.10
Monitoring 56
4.3.11
Review process and adaptive management 57
4.4 Implementing environmental water provisions
58
5. Guidelines for Groundwater Dependent Ecosystem Policy60
5.1 Introduction
60
5.2 National groundwater policy
60
5.3 Environmental water provisions policy
61
5.4 Proposed national principles for water allocation
to groundwater dependent ecosystems
62
6. Groundwater Management Planning for Dependent
Ecosystems
6.1 Introduction
6.2 New South Wales
6.3 Northern Territory
6.4 Queensland
6.5 South Australia
6.6 Tasmania
6.7 Victoria
6.8 Western Australia
6.9 International Approaches
67
67
67
68
68
69
69
70
70
73
7. Economics of Protecting Groundwater Dependent
Ecosystems
75
7.1 Introduction
75
7.2 Policy background
75
7.3 Economic impacts of groundwater dependent
ecosystem management
75
7.3.1
Costs 76
7.3.2
Benefits 78
7.3.3
Discussion 79
7.4 Evaluating the economic costs and benefits of
conserving groundwater dependent ecosystems
80
7.4.1Benefits of groundwater dependent ecosystem managemen
7.4.2Costs of groundwater dependent ecosystem management
7.4.3
Benefit cost assessment 83
8. Conclusions
85
9. Recommendations
89
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10.
References 90
11.
Glossary 97
12.
Acknowledgments 98
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Document History and Status
Issue
Rev.
Issued To
Qty
Date
Reviewed
Approved
Draft
A
G.Stewart,
T.Hatton,
R.Froend, A.Spate,
C.Gippel
G.Stewart
5
25.08.2000
R.Evans
R.Evans
2
04.10.2000
T.Hatton,
R.Froend, A.Spate,
C.Gippel, K.Olsson
R.Evans
Final
Printed:
Last Saved:
File Name:
Project Manager:
Name of
Organisation:
Name of Project:
Name of Document:
Document Version:
Project Number:
4 October 2000 12:55 PM
30 October 2000 5:13 PM
I:\WCMS\WC01191\REP00_01.10\r01cac_gde_final.doc
Dr. Richard Evans
Environment Australia
Environmental Water Requirements of Groundwater Dependent
Ecosystems
Project Report
Final
WC01191
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Executive Summary
Introduction:
The National River Health Program aims to help build
the foundation for protection of Australia’s water
resources. As a component of the Program, Environment
Australia has commissioned this project to define
issues relating to the environmental water requirements
of groundwater dependent ecosystems. The project deals
with three stages in the process of allocating
groundwater to meet the needs of dependent ecosystems,
as follows:
Groundwater
dependency
Environmental
water
requirement
(EWR)
Environmental
water
provision
(EWP)
Determine the important groundwater
dependent ecosystems and the nature of
threats to key e ologi al pro esses
Develop a process by which the water
regimes needed to sustain key
ecological values of groundwater
d
d
l
l
l f
Develop a process for groundwater
allocation that balances water
requirements to sustain key ecological
values of dependent ecosystems and
broader so ial and e onomi obje tives
Groundwater dependent ecosystems:
The groundwater dependent ecosystems of Australia
represent a diverse, yet distinct component of the
nation’s biological diversity. Six major types have
been identified:
terrestrial vegetation – vegetation communities and
dependent fauna that have seasonal or episodic
dependence on groundwater;
river base flow systems – aquatic and riparian
ecosystems that exist in or adjacent to streams that
are fed by groundwater base flow;
aquifer and cave ecosystems – aquatic ecosystems that
occupy caves or aquifers;
wetlands – aquatic communities and fringing
vegetation dependent on groundwater fed lakes and
wetlands;
terrestrial fauna – native animals that directly use
groundwater rather than rely on it for habitat;
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estuarine and near-shore marine ecosystems – coastal,
estuarine and near shore marine plant and animal
communities whose ecological function has some
dependence on discharge of groundwater.
Australia has a diverse set of groundwater dependent
ecosystems. Cave and aquifer ecosystems, particularly,
are very specialised and characterised by high levels
of endemism. Groundwater dependent ecosystems vary from
being marginally or only episodically dependent on
groundwater (e.g. some terrestrial vegetation) to being
entirely groundwater dependent (e.g. mound springs and
the aquatic ecosystems of caves and aquifers).
Ecological processes in these ecosystems depend on
water regimes involving the:
level or pressure of groundwater
discharge flux from an aquifer
quality of water.
The water regime for some dependent ecosystems may also
be characterised by variability in time.
Threatening processes:
Ecological processes in groundwater dependent
ecosystems are threatened by the use or extraction of
groundwater and changes in land use or management. The
major threatening processes are considered to be:
groundwater resource development
changes in land use – particularly from native
vegetation to agriculture or agriculture or native
vegetation to plantation forestry
activation of acid sulphate soils in coastal areas by
drainage, dredging or groundwater extraction
dewatering or water resource development associated
with mining
commercial, urban or recreational developments.
These activities have potential to alter the water
regime experienced by groundwater dependent ecosystems.
This may in turn produce changes in the structure,
function and/or composition of the ecosystem. More
highly dependent ecosystems and those that occupy a
very narrow ecological range may be completely
eliminated by even relatively small changes in water
regime.
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Important groundwater dependent ecosystems:
A system of classification has been developed for
groundwater dependent ecosystems. Importance was
expressed in terms of the conservation value of the
ecosystem, its vulnerability to potential threats and
the likelihood of threats being realised. Groundwater
dependent ecosystems receiving a high classification
are indicated in the following table.
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Threat to ecosystem
Ecosystem
Process
Vulnerabil
ity
Groundwater Impact if
attribute
threat
realised
Risk
Value
Likelihood Conservati
of threat
on value
being
of
realised
ecosystem
Entirely dependent on groundwater
•
Mound spring ecosystems
Water resource
Pressure
High
High
High
•
Karstic groundwater ecosystems
Level,
quality
High
High
High
•
Permanent lakes and wetlands of
Swan Coastal Plain
Level,
quality
High
High
Moderate
•
Pilbara spring ecosystems
Level,
quality
High
Moderate
High
•
Inland mangrove near 80 Mile
Beach in Western Australia
Arid zone groundwater calcrete
ecosystems
Riverine aquifer ecosystems
Water resource,
agriculture,
mining
Urban &
commercial, water
resources
Mining, water
resource,
agriculture
No major current
threat
Water resource,
mining
Water resource,
agriculture, urban
& commercial
development
Water resource,
mining
Level
High
Low
High
Level,
quality
Level,
quality
High
Moderate
High
High
High
Moderate
Level,
quality
High
Moderate
High
Water resource,
mining,
agriculture
Urban &
commercial, water
resource
Water resource,
agriculture,
forestry
Water resource,
urban & commercial
Level,
quality
High
Moderate
Moderate
Level,
quality
High
Moderate
High
Level,
quality
Moderate
High
Moderate
Level,
quality
High
High
Moderate
Permanent coastal lake, dune and
beachridge plain ecosystems of
coastal NSW and coastal sand
islands of NSW and Qld.
• Phragmites and Typha communities
of permanently flooded swamps
and lakes of inland areas of the
south-eastern uplands,
• Permanent base flow dependent
swamps and river pools of
Kangaroo Island
• Riparian swampland communities
of Mount Lofty Ranges
• Swan Coastal Plain damplands and
sumplands with paperbark and
Banksia woodlands
• Coastal swamp scrub sedgeland
communities in the near-coastal
dune systems of the Upper South
East of South Australia
Ecosystems with opportunistic
groundwater dependence
Urban &
commercial, water
resource, acid
sulphate soils
Water resource,
agriculture
Level,
quality
High
High
Moderate
Level,
quality
High
High
Moderate
Water resource,
agriculture
Moderate
High
Moderate
Water resource,
agriculture
Water resources,
urban & commercial
Level,
quality,
Flux
Level,
quality
Level,
quality
Moderate
High
Moderate
High
High
Moderate
Agriculture
Level
High
Moderate
Moderate
•
Agriculture, water
resources
Level,
quality
Moderate
High
High
•
•
•
Marine tide influenced cave (or
anchialine) ecosystems
Highly dependent on groundwater
•
Pilbara river pool ecosystems
•
Near shore stromatolites of
coastal Western Australia
•
Groundwater dependent wetlands
of basalt plains of Western
Victoria
Damplands of Swan Coastal Plain
•
Proportionally dependent ecosystems
•
Ecosystems of the Coorong
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•
•
Ecosystems of permanent lakes
and swamps at termini of inland
rivers in the Central Lowlands
and South Australian Ranges
Major ocean embayments such as
Port Phillip Bay
Agriculture, water
resource
Level
Agriculture, urban
& commercial, acid
sulphate soils
Flux,
level,
quality
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High
Moderate
Moderate
Moderate
High
Moderate
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Defining Environmental Water Requirements:
The environmental water requirement (EWR) of a
groundwater dependent ecosystem is the water regime
needed to sustain its key ecological values. The EWR
is analogous to the environmental flow requirement
concept for surface water dependent ecosystems. The
environmental water requirement of groundwater
dependent ecosystems must be understood if the
management of groundwater resources is to be consistent
with the principles of ecologically sustainable
development.
Environmental water requirements may be derived from an
understanding of four key factors:
the nature of ecosystem dependency on groundwater
the water requirements of the ecosystem
the groundwater regime that will satisfy the water
requirements of the ecosystem
the impacts of change in groundwater regime on
ecological processes.
A conceptual framework for the process by which these
information requirements may be met and, in effect, the
environmental water requirements of groundwater
dependent ecosystems determined has been developed.
This framework can be applied in a range of operating
environments, from those that are tightly constrained
by poor information and resource availability to those
that are not. The environmental water requirement would
largely be determined by literature review and expert
opinion where resources are limited and by a
combination of these approaches and direct
investigation where time and resources allow.
There are very few case studies in Australia where the
environmental water requirement of groundwater
dependent ecosystems have been determined through
direct field research. A key knowledge gap for
environmental water requirement determination is the
response of dependent ecosystems to change in
groundwater regime.
Environmental water provisions
Many groundwater dependent ecosystems exist in
environments that have been modified by human activity.
The groundwater that at least in part sustains these
ecosystems has other values, particularly the provision
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of water for agriculture, urban or industrial use.
While the environmental uses of groundwater are
increasingly being recognised, they are inevitably
balanced against the social and economic benefits of
non-environmental uses.
Processes are required to define an Environmental Water
Provision (EWP), a water regime that is maintained with
the objective of sustaining key ecological values of
groundwater dependent ecosystems, but which recognises
economic, social and ecological goals. Three approaches
have been applied to making environmental water
provisions for groundwater dependent ecosystems:
no specific provision –traditionally, groundwater
resource allocation in many areas has ignored the
requirements of groundwater dependent ecosystems and
made no provision for a water regime that might
sustain them.
fixed environmental water provision – blanket
environmental water provisions may be applied such
that a fixed percentage of average annual groundwater
recharge (for example) is allocated to provide a
water regime intended to meet the needs of dependent
ecosystems.
environmental water provision based on consideration
of environmental water requirement – the water regime
necessary to meet the environmental water requirement
of the groundwater dependent ecosystem is assessed.
Allocation decisions are made through an process
which is informed by an understanding of their
economic, social and environmental costs and
benefits.
A framework for the determination of environmental
water provisions that is based on an explicit
consideration of ecosystem water requirements has been
developed. It generally follows a “best practice”
framework developed for environmental flows for surface
water systems. Its key elements include:
determination of the environmental water requirement;
stakeholder participation to identify economic,
social and environmental objectives for the
groundwater resource;
balancing considerations of the condition and value
of the ecosystem with the environmental, economic and
social impacts of providing a range of water regimes,
some of which meet the ecosystem’s environmental
water requirements;
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a system of monitoring, review and adaptive
management.
Implementation of environmental water provisions
depends on there being commitment by State groundwater
and natural resource management agencies to make such
provisions and to adequately resource investigations
that would be required to support environmental water
provision determinations.
Economics of groundwater dependent ecosystems:
An estimate of the economics of conserving groundwater
dependent ecosystems on a national level has been
undertaken using a rapid evaluation approach. This
approach provides an approximate and very coarse
indication of the economic viability of conservation.
Based on some broad assumptions, the costs of
groundwater dependent ecosystem management were
estimated to be in the range $112 - $225 million per
annum. This estimate is based on the potential cost of
reducing water use sufficiently to make environmental
water provisions for groundwater dependent ecosystems
at a national level. The cost per household is at least
2 to 3 times what households have indicated they are
willing to pay for protecting other types of natural
areas. However, on a per hectare basis, these costs are
roughly equivalent with the amounts consumers are
willing to pay for the protection of other similar
natural areas.
Groundwater dependent ecosystem policy:
The Coalition of Australian Governments’ Water Reform
Framework Agreement provides a policy context for the
sustainable use of water resources through provision of
water to meet the environmental needs of dependent
ecosystems. Under this framework, a set of principles
for the provision of water for the environment have
been developed. However, the language used is most
applicable to surface water dependent systems.
These principles have therefore been reworded (see
table below) to reflect the specific issues associated
with groundwater dependent ecosystems.
Goal:
The goal for providing water for the environment is to sustain and where
necessary restore ecological processes and biodiversity of groundwater
dependent ecosystems.
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Principles:
1.
Groundwater abstraction and consumptive use, surface water regulation
and consumptive use, as well as land use practices, should be
recognised as potentially impacting on ecological values of
groundwater dependent ecosystems.
2.
Provision of environmental water should be on the basis of the best
scientific information available on the groundwater regimes, in terms
of flux, level, pressure and/or quality, necessary to sustain the
ecological values of dependent ecosystems. It must include the
identification of key ecological values and processes for groundwater
dependent ecosystems. Where relevant, provision of environmental water
for groundwater dependent ecosystems should integrate groundwater and
surface water requirements. Where information on environmental water
requirements is limited, the precautionary principle should be adopted
in setting interim environmental water provisions, should they be
required.
3.
Environmental groundwater provisions should be legally recognised.
They should form part of estimates of sustainable yield in groundwater
management planning and not generally be tradeable in any water
entitlement market.
4.
Where there are existing users of an aquifer or groundwater basin,
provision of water for dependent ecosystems should go as far as
possible to meet the water regime necessary to sustain their
ecological values whilst recognising the needs of existing water
users.
5.
Where environmental water requirements cannot be met due to existing
uses, action (including reallocation) should be taken to meet
environmental needs. If environmental water requirements cannot be met
without substantially compromising the economic and social benefits of
existing consumptive uses, the environmental risks of not meeting the
ecosystem water requirements and the social and economic costs of
meeting them should be identified and considered in water allocation
planning decision making processes.
6.
Further allocation of water for any use should only be on the basis
that natural ecological processes and biological diversity are
sustained.
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Principles (cont):
7.
In proposing environmental water provisions for groundwater dependent
ecosystems, consideration will be given to environmental changes that
have occurred with historical abstraction, resource management, land
use, water quality impact and/or the capacity for restoration of
altered ecosystems.
8.
Accountabilities in all aspects of management of environmental water
provisions for groundwater dependent ecosystems should be transparent
and clearly defined.
9.
Environmental water provisions should be adaptive, responding to
monitoring, improvements in understanding of environmental water
requirements and/or ecological significance of dependent ecosystems
and to changing demand for consumptive use.
10. All water uses should be managed in a manner that recognises
ecological values.
11. Appropriate demand management and water pricing strategies should be
used to assist in sustaining ecological values of water resources.
12. Strategic and applied research to improve understanding of
environmental water requirements of groundwater dependent ecosystems
is essential.
13. All relevant environmental, social and economic stakeholders will be
involved in water allocation planning and decision-making on
environmental water provisions for groundwater dependent ecosystems.
Groundwater planning:
There is wide variability between the groundwater
planning processes used in each of the Australian
states and territories. This is particularly true in
the provision of water for groundwater dependent
ecosystems. There is a strong emphasis on environmental
water provisions in groundwater allocation planning in
Western Australia, New South Wales and South Australia.
Attention to the water requirements of these ecosystems
is modest in other states and territories. The
potential implications of this are greater in
Queensland and Victoria, where many groundwater
management units are over-allocated, despite the
current lack of explicit provision of water for
environmental purposes.
Recommendations:
It is recommended that Commonwealth and State
governments make further investment in research and
investigations to:
identify groundwater dependent ecosystems;
determine the conservation status of groundwater
dependent ecosystems, particularly those ecosystems
most threatened by groundwater resource development
and land use factors;
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develop a priority ranking of groundwater dependent
ecosystems, based on conservation status and
vulnerability to and risk of changed water regime;
understand the response of key groundwater dependent
ecosystems to changes in their water regime.
It is recommended that State and Territory groundwater
resource management agencies incorporate the following
in the allocation planning processes:
specific provision of water to meet the environmental
requirements of groundwater dependent ecosystems;
integrated consideration of the environmental
requirements of surface water and groundwater
dependent ecosystems where groundwater and surface
waters interact;
processes to determine the environmental requirements
of groundwater dependent ecosystems;
processes that make environmental provisions based on
an understanding of the water regime required to
sustain ecological processes in dependent ecosystems;
processes that make environmental provisions that are
transparent, participative and based on a thorough
assessment of the social, economic and environmental
implications of those provisions.
It is further recommended that a set of national
principles for water allocation for groundwater
dependent ecosystems be prepared and adopted by all
State and Territory governments.
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1. Introduction
1.1 Introduction
The National River Health Program (NRHP) aims to help
build the foundation for protection of Australia’s
water resources. As a component of the NRHP,
Environment Australia (EA) has commissioned this report
to define issues relating to the environmental water
requirements of groundwater dependent ecosystems
(GDEs).
The concept of making provision of water for
environmental purposes is not a new one. Environmental
flow allocations for surface water systems have been
considered in Australia for a decade or more and there
is an extensive national and international literature
on the topic (see Arthington and Zalucki 1998). By
contrast there is limited, although growing, experience
in the provision of water to meet the needs of
groundwater dependent ecosystems.
Groundwater resources in many parts of Australia are
facing increasing pressure from consumptive uses for
agricultural, mining, urban and commercial
developments. The water regimes and water quality
experienced by groundwater dependent ecosystems are
changing due to consumptive uses and to other land use
and management factors. Collectively, anthropogenic
changes in groundwater regime pose a significant, but
largely unknown threat to groundwater dependent
ecosystems. That threat will be maintained and may
ultimately be realised unless specific actions are
taken to provide these ecosystems with appropriate
water regimes.
Like other forms of natural resource management,
groundwater resource management is required to operate
according to the principles of Ecologically Sustainable
Development. To do so, groundwater resources must be
managed in ways that are consistent with the principles
of conservation of biological diversity, namely:
conservation of biodiversity should take place in
situ;
action to conserve biodiversity must not be postponed
in the absence of full knowledge;
the establishment of a comprehensive, representative
and adequate system of ecologically viable protected
areas;
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sympathetic management of other landscapes, including
those in which agricultural and other resource
production systems operate.
(after Government of Australia 1996)
If groundwater resource management is to be consistent
with these principles, then allocation processes must
consider the environmental needs of dependent
ecosystems. Where appropriate they must also ensure
that water is provided to meet the needs of key
ecological functions in groundwater dependent
ecosystems.
This report deals with the three main stages in the
process of allocating groundwater to meet the needs of
dependent ecosystems. These stages and key terms are
defined in Figure 1.1. The report also proposes a
policy framework for this process that could be adopted
at national and state levels.
Figure 1.1: Allocating water to meet the environmental
needs of groundwater dependent ecosystems: the key
stages.
Groundwater
dependency
Environmental
water
requirement
(EWR)
Environmental
water
provision
(EWP)
Determine the important ecosystems whose
ecological processes are at least partly
sustained by groundwater, the nature of
their dependen y on groundwater and threats
Develop a process by which the water
regimes needed to sustain key ecological
values of groundwater dependent ecosystems
l
l
l f i k
d
i d
Develop a process for groundwater
allocation that balances water requirements
to sustain key ecological values of
dependent ecosystems and broader social and
e onomi obje tives for the resour e
Adapted from Water and Rivers Commission (1999).
1.2 Study objectives
The objectives of the project were defined in the study
brief prepared by Environment Australia. They were to:
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identify those important groundwater dependent
ecosystems in Australia that are at high risk of
degradation from current or future changes in
catchment hydrology;
determine the processes involved in alteration of
these systems, especially the impact of water
extraction;
develop a method for determination of environmental
water requirements that will protect these systems
against decline in their ecological character;
identify information gaps in determining
environmental water requirements of groundwater
dependent ecosystems;
identify the practical limitations and opportunities
available for implementation of environmental water
requirements to these systems;
identify primary economic drivers for implementing
water management regimes to protect groundwater
dependent ecosystems;
describe a framework for assessing the economic
feasibility of implementing management regimes.
1.3 Structure of report
The report has been structured to follow a progression
in information and analysis; from the provision of
background information on Australian groundwater
dependent ecosystems, through the description of
processes by which their environmental water
requirements might be determined, to the provision of
guidelines for groundwater policy and planning in
relation to the provision of water to meet those
requirements.
Contents of the remaining sections of the report are
described below:
Section 2: Australian groundwater dependent
ecosystems – discussion of the forms of groundwater
dependency, types of groundwater dependent ecosystems
in Australia and the processes threatening them.
Overview of key threatened groundwater dependent
ecosystems in Australia.
Section 3: Environmental water requirements of
groundwater dependent ecosystems – description of a
framework for determining the environmental water
requirements of groundwater dependent ecosystems.
Section 4: Environmental water provisions for
groundwater dependent ecosystems – description of a
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framework for assessing environmental water
provisions for groundwater dependent ecosystems.
Section 5: Guidelines for groundwater dependent
ecosystem policy – development and discussion of some
proposed principles for policy in relation to
groundwater dependent ecosystems.
Section 6: Groundwater management planning –
discussion of national and international approaches
to groundwater planning for the provision of
environmental water for groundwater dependent
ecosystems.
Section 7: Economics of protecting groundwater
dependent ecosystems –identification and preliminary
assessment of the economic impacts of management
practices designed to protect groundwater dependent
ecosystems
Section 8: Conclusions – summary of key findings of
project.
Section 9: Recommendations – summary of major
recommendations from project.
Section 10: References - literature cited in
preparation of this report.
Section 11: Glossary – definition of some key terms
used in the report.
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2. Australian Groundwater Dependent Ecosystems
Groundwater dependent ecosystems represent a small, but
diverse and important component of Australia’s
biological diversity. Their recognition as a distinct
group is relatively recent and may largely be
attributed to work by Hatton and Evans (1998).
This section of the report provides an overview of
groundwater dependent ecosystems in Australia. It draws
heavily on the work of Hatton and Evans (1998). The
forms of groundwater dependency and major anthropogenic
processes that threaten ecological function in those
ecosystems are described. The section concludes by
providing a preliminary assessment of the relative
importance or priority for management of some of the
more prominent ecosystems.
2.1 Ecosystems and groundwater dependency
The dependency of ecosystems on groundwater is based on
one or more of four basic groundwater attributes:
flow or flux – the rate and volume of supply of
groundwater;
level – for unconfined aquifers, the depth below
surface of the water table;
pressure – for confined aquifers, the potentiometric
head of the aquifer and its expression in groundwater
discharge areas;
quality – the chemical quality of groundwater
expressed in terms of pH, salinity and/or other
potential constituents, including nutrients and
contaminants.
The response of ecosystems to change in these
attributes is variable. There may be a threshold
response in some cases, whereby an ecosystem collapses
completely if a certain attribute value is exceeded.
Examples might be individual mound spring communities
supported by groundwaters of the Great Artesian Basin
(GAB). These would cease to exist if pressures in the
GAB fell to the point where there was no further
surface discharge. In other cases a more gradual change
in the health, composition and/or ecological function
of communities is expected as, for example, may occur
with increasing groundwater salinity or contaminant
concentration.
Hatton and Evans (1998) recognised five classes of
ecosystem dependency on groundwater, as follows:
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Ecosystems entirely dependent on groundwater –
communities where only slight changes in key
groundwater attributes below or above a threshold
would result in their demise. Examples include
ecosystems with very narrow ecological ranges for
water quality or groundwater level or pressure, those
dependent entirely on surface or near surface
discharge of groundwater for survival and aquatic
ecosystems whose habitat is groundwater or entirely
groundwater derived.
Examples of entirely dependent ecosystems include the
mound spring systems of the GAB, karstic groundwater
ecosystems of the Cape Range and at Yanchep in
Western Australia, channel waterholes in the Central
Australian ranges, saline discharge lakes of the
western Murray Basin, riparian vegetation along
streams in the central Australian arid zone,
permanent wetlands of the Swan Coastal Plain, spring
ecosystems of the Pilbara and Central ranges and the
arid zone calcrete aquifer ecosystems of central
Western Australia.
Ecosystems highly dependent on groundwater –
communities where moderate changes in groundwater
discharge or water tables would result in a
substantial change in their distribution, composition
and/or health. Such ecosystems utilise both
groundwater and surface and/or soil water. They would
be substantially modified (at least) if the supply of
groundwater ceased.
Examples of highly dependent ecosystems include:
mesophyll Palm forests and Melaleuca swamp forests
and woodlands of tropical northern Australia,
woodland communities of solution hollows of the Eyre
and Yorke Peninsulas, many karst ecosystems,
permanent waterholes and river pool systems along the
stream systems of central and north western
Australia, near shore stromatolite systems of coastal
Western Australia, wetlands of the basalt plains in
Victoria, base flow dependent ecosystems of southeastern Australia and the damplands of the Swan
Coastal Plain.
Ecosystems with proportional dependence on
groundwater – such ecosystems do not exhibit the
threshold-type responses of the more highly dependent
ecosystems. Rather as the relevant groundwater
attribute changes, there is a proportional response
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in the ecosystem, particularly in terms of
distribution.
A large number of examples of this type of ecosystem
were identified by Hatton and Evans (1998). Many of
them are base flow and permanent lake ecosystems.
They are found throughout Australia in environments
as diverse as glacial lakes and alpine bogs in upland
areas, lakes and riparian zones along Tasmanian
rivers to uplands of the north-east and north
Australia and Kimberley plateaux and coastal
vegetation communities of Gippsland, northern New
South Wales and the sandy islands off the southern
Queensland coast.
Ecosystems that make limited or opportunistic use of
groundwater – groundwater appears only to play a
significant role in the water balance of such
ecosystems at the end of a dry season or during
extreme drought. In the short term, communities may
tolerate lack of access to suitable groundwater,
however they will decline and ultimately collapse if
this state is prolonged excessively.
Examples of opportunistic ecosystems include, swamp
forests of coastal floodplains along the fringe of
the south-east uplands, Jarrah forests and Banksia
woodlands of south-west Western Australia, lignum
shrublands of inland river systems, ecosystems of the
Coorong, ecosystems of the terminal lakes and
wetlands of Central Australian river systems, major
near shore ecosystems of ocean embayments, such as
Port Phillip Bay and coast mangrove and salt marsh
ecosystems.
There are a range of wetland and riparian ecosystems in
Australia that might superficially appear to be
groundwater dependent, but are considered to be either
entirely rainfed or dependent only on surface water
flows. This category was included by Hatton and Evans
(1998) to emphasise that there are some ecosystems
which might initially appear to be groundwater
dependent, but upon further examination prove not to
be. Examples of this type of ecosystem include seasonal
floodplain lakes on small creeks in northern Australia,
Phragmites grasslands at the mouth of the Murray River,
in-stream ecosystems of the Murray and Darling Rivers,
terminal drainage basin lakes in the Central Lowlands
(e.g. Cobham Lake, Lake Bancania), intermittent and
episodic wetlands and lakes of the arid zone and of the
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Western Australian sandplain and Yilgarn Plateau, rock
pools and solution hollows of the Nullarbor Plain and
southern rainforests.
2.2 Australian groundwater dependent ecosystems
There is a substantial body of literature on the
ecology of groundwater dependent ecosystems in
Australia. Hatton and Evans (1998) reviewed much of
this literature and concluded that most was based on
investigations undertaken from a purely ecological
perspective. Few studies considered groundwater
processes and specific details of ecosystem or
community dependency on groundwater.
The three main examples of systems in which groundwater
dependency have been considered in some detail are the
mound springs of the Great Artesian Basin (e.g. Ponder
and Herschler 1984; Ponder 1985; 1986; Boyd 1990),
wetlands of the Swan Coastal Plain (e.g. Farrington et
al. 1990; Hill et al. 1996 a,b) and riparian and flood
plain woodlands of the lower Murray river system (e.g.
Thorburn and Walker 1994; Mensforth et al. 1994).
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Hatton and Evans (1998) identified four types of
groundwater dependent ecosystem:
terrestrial vegetation;
river base flow systems;
aquifer and cave ecosystems;
wetlands.
It has since became apparent that there are at least
two additional distinct types of groundwater dependent
ecosystem, namely:
terrestrial fauna;
estuarine and near-shore marine ecosystems.
The following sections contain a brief overview of each
of the six broad classes of groundwater dependent
ecosystem. The discussion also considers the nature of
the interaction between each type of ecosystem and
groundwater. Much of the material presented has been
drawn from Hatton and Evans (1998).
2.2.1 Terrestrial vegetation
This class of groundwater dependent ecosystem includes
vegetation communities that do not rely on expressions
of surface water for survival, but which have seasonal
or episodic dependence on groundwater. Groundwater
systems may be locally recharged during a pronounced
wet season, such as the upland sclerophyll woodlands of
northern Australia and the Jarrah forests and Banksia
woodlands of south-western Australia. Eucalypt
woodlands on the Eyre Peninsula and along the flood
plain of the Murray River may access shallow local or
regional groundwater systems.
Terrestrial vegetation communities are among those most
threatened by changes in groundwater level associated
with irrigated and dryland agricultural land use. This
is particularly true for small patches of remnant
vegetation and those in areas where regional
groundwater levels have risen substantially since
European settlement. Greater recharge under
agricultural land use has meant that groundwaters may
now be permanently within the root zone of the
vegetation and sufficiently shallow for direct
evaporative discharge to salinise the soil (e.g. Jolly
et al. 1993 for E.largiflorens woodlands on Murray
River floodplain).
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Terrestrial vegetation communities are influenced by
several of the key groundwater attributes, as follows:
Level – most terrestrial groundwater dependent
ecosystems require groundwater levels in unconfined
aquifers to be at least episodically or periodically
within their root zone. Groundwater would typically
be required to satisfy evaporative demand during
times when soil water availability is low. These
communities would also rely on moderately or highly
saline groundwater not remaining at such a high level
that the soil profile (and plant root zone) became
salinised.
Flux – in addition to being at a level accessible to
plant roots, groundwater flux would need to be
sufficient to sustain a level of uptake by vegetation
that at least partly satisfied evaporative demand.
Quality – salinity would typically be the key
indicator of groundwater quality for such ecosystems.
However, if groundwater dependent, the ecosystem is
likely to be relatively salt tolerant. Terrestrial
ecosystems may also be sensitive to groundwater
contamination by nutrients, pesticides or heavy
metals, however little is known of their response.
2.2.2 Wetlands
Groundwater dependent wetland ecosystems are those that
are at least seasonally waterlogged or flooded. Hatton
and Evans (1998) considered that they provided the most
extensive and diverse set of potentially dependent
ecosystems in Australia. For the purposes of this
report, freshwater groundwater dependent wetlands will
be considered separately from estuarine or marine
systems (described in section 2.2.3).
Examples of groundwater dependent wetland ecosystems
include:
Mesophyll palm vine forests – which occur in small
patches or more extensive stands in tropical northern
Australia and were considered likely by Hatton and
Evans (1998) to have some dry season dependency on
groundwater.
Paperbark swamp forests and woodlands – these
ecosystems are widely distributed across coastal dune
and coastal and river flood plain areas of northeastern, northern Australia and south-western
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Australia. They are typically found in low-lying
positions that are either seasonally inundated or are
at the margins of rivers or lakes that are at least
partly groundwater derived.
Swamp sclerophyll forests and woodlands – another
widely distributed group of ecosystems that exhibit
at least seasonal dependency on groundwater. They
include a wide range of mostly eucalypt species that
occupy the riparian corridors of ephemeral or baseflow dependent streams. The group includes species
such as E.ovata, E.viminalis and E.leucoxylon
communities in South Australia, E.camaldulensis and
E.largiflorens woodlands of the Murray and Darling
River floodplain and of the inland river systems of
central Australia.
Swamp scrubs and heaths – this type of ecosystem
normally occupies sandy or peaty soils in landscapes
ranging from coastal dunes to swampy areas fed by
snow melt in the southern Australian highlands.
Farrington et al. (1990) found substantial use of
groundwater by swamp scrub on the sumplands and
damplands of the Swan Coastal Plain in Western
Australia.
Swamp shrublands – Lignum (Meuhlenbeckia
cunninghamii) dominated shrublands are common
features of the inland ephemeral stream and lake
systems of southern and northern Australia.
Groundwater dependency is suspected, but has not been
thoroughly investigated (Hatton and Evans 1998).
Similarly, chenopod shrublands of the heavy-textured,
periodically inundated plains country of western New
South Wales and Queensland and northern South
Australia are suspected of being groundwater
dependent, but without any clear indication of the
nature of that dependency.
Sedgelands – there are a great array of sedgeland
communities in the coastal, floodplain and valley
floor environments of eastern Australia. Most require
at least seasonal waterlogging. Those that require
permanent surface wetness are almost certainly
groundwater dependent (e.g. Eleocharis sphacelata
sedgelands in lagoons of the Murray River and
tributaries, Baumea sedgelands of the Coorong and
south-east of South Australia, and Button Grass
Gymnoschoenus spaerocephalus sedgelands of Tasmania’s
south-west).
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Swamp grasslands – wet grassland communities are most
extensive in northern Australia on heavy, seasonally
flooded soils, however they appear not to exhibit
groundwater dependency (Hatton and Evans 1998).
Phragmites and Typha grasslands are common in
seasonally and permanently waterlogged locations
across eastern and southern Australia. Their
groundwater dependency was considered by Hatton and
Evans (1998) to vary widely, with those communities
associated with groundwater dependent semi-permanent
water features to be the most likely to exhibit
dependency.
Swamp herblands – Hatton and Evans (1998) noted that
floating and floating leaved herblands are common in
coastal rivers and dune swales and lakes throughout
Australia. The characteristic wetness of the
locations implies some role for groundwater and
associated ecosystem dependency.
Mound springs ecosystems – mound springs of the GAB
support a diverse group of ecosystems that are
entirely groundwater dependent. The most common
vegetation associations are grasslands and
sedgelands, although some larger spring pools support
Melaleuca glomerata swamp woodlands or scrublands.
The springs also support endemic fish and
invertebrate species.
The diversity of groundwater dependent wetland
ecosystems means that each of the four key groundwater
attributes would play some role in their dependency.
For the majority of ecosystems, groundwater level in
unconfined aquifers and groundwater discharge flux
would need to be adequate to ensure that the required
state of wetness or waterlogging was maintained at key
ecological stages. Species and communities requiring
permanently wet conditions, particularly in arid, semiarid or seasonally dry conditions would be more likely
to be groundwater dependent than those tolerant of a
regular cycle of wetting and drying. Groundwater
pressure in mound springs ecosystems would have a
similar degree of importance.
Changes in water table level may have important
implications for these communities. Prolonged lowering
or raising of the water table are likely to result in
changes in species composition, to favouring species
adapted to drier or wetter conditions, respectively.
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Groundwater resource development on the Swan Coastal
Plain of Western Australia has resulted in lowered
water tables in some areas and contributed to a decline
in the local swamp scrubs and heaths. As with
terrestrial vegetation, the development of more shallow
saline groundwaters may result in the salinisation of
plant root zone and the subsequent collapse of
ecosystems.
2.2.3 Estuarine and near shore marine systems
These types of ecosystem are the marine counterparts of
the ecosystems described in section 2.2.2. A variety of
groundwater dependent ecosystems are described in the
literature. Several examples are listed below.
Coastal mangroves and salt marshes – mangroves are
widely distributed around the Australian coast. While
most common in northern Australia, they may be found
as far south as Corner Inlet in Victoria. While
seawater is considered to be the primary water source
for most of these vegetation communities, sites have
been noted where mangroves occupy discharge areas for
relatively fresh groundwater (Adam 1994). The extent
of groundwater dependency is unknown.
Salt marshes tend to replace mangroves in coastal
locations in southern Australia. The nature of any
groundwater dependency is unknown.
Protection of coastal mangroves and salt marshes from
clearing and drainage may play an important role in
maintaining groundwater discharge and preventing the
activation of acid sulphate soils.
Coastal lakes – coastal lakes along the south-west
coastline of Western Australia support the
development of stromatolites and have quite varying
aquatic communities. Groundwater is the principal
source for many of the lakes. Some Victorian coastal
lakes and wetlands maintain fresh to brackish species
compositions due to the discharge of relatively fresh
groundwater.
Sea grass beds – the distribution of sea grass beds
in some coastal areas is influenced by groundwater
discharge (PPK 1999).
Marine animals – some marine and estuarine animals
depend on groundwater discharge to provide a suitable
habitat or an appropriate environment in which
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species of plant and/or animal they eat will prosper.
Groundwater discharge may be in the form of direct
off-shore discharge or base flow into streams that
discharge to the ocean. Examples of groundwater
dependent fauna include crocodiles, turtles, fish and
macro-invertebrates (Hatton and Evans 1998; PPK 1999;
Sinclair Knight Merz 2000).
Groundwater flux will strongly influence dependency of
coastal and estuarine ecosystems. Direct discharge
fluxes and/or base flow volumes would need to occur at
a sufficient rate that groundwater significantly
dilutes seawater.
Many coastal ecosystems face increasing threat from
groundwater contamination and water quality decline.
Urban, commercial and tourism developments and
intensive agricultural land use are important risk
factors in many coastal areas. Groundwater could be
contaminated by nutrients from fertilisers and septic
tank effluent, agricultural pesticides and metals and
hydrocarbons from commercial and urban land uses.
Exposure to contaminants poses direct short and long
term threat to ecological processes. Elevated nutrient
levels may result in algal blooms that could render (at
least temporarily) marine and estuarine habitats
unsuitable for key species.
Groundwater level in some coastal aquifers will
strongly influence ecosystem health. Acid sulphate
soils are activated when iron sulphides in the soil are
exposed to oxygen if groundwater levels are lowered by
drainage, groundwater pumping or drought (see section
2.3.3). The consequent very acid drainage waters from
these soils may result in sensitive species being
killed or displaced. Flocculation of iron in the water
may result in aquatic or marine communities being
smothered.
2.2.4 River base flow systems
This category of ecosystem was devised by Hatton and
Evans (1998) to include the many ecosystems that are
dependent on groundwater derived base flow in streams
and rivers. Base flow is that part of stream flow
derived from groundwater discharge and bank storage.
Dry season flows in permanent and semi-permanent
streams in northern Australia may be almost entirely
provided by base flow. Base flow also contributes to
wet season flows in such streams, but not to the same
extent (Cook et al. 1998).
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Base flow may contribute year round to flows in coastal
streams in south-eastern Australia and may contribute
to flow in inland streams, although the extent of the
contribution may be difficult to determine in some
cases due to river regulation (Hatton and Evans 1998).
Riparian and aquatic ecosystems in base flow dependent
streams would be, to a greater or lesser extent,
groundwater dependent themselves. Demarcation between
groundwater dependent terrestrial vegetation, wetlands
and base flow systems may be difficult, with the three
types of community representing ranges on a spectrum of
habitat, groundwater and surface water dependency.
The coastal rivers from the north-west of Australia to
the north-east are considered to be base flow dependent
during the dry season (Hatton and Evans 1998). They
support a rich assemblage of wetland and in-stream
ecosystems, which include streamside forests and
woodlands, as well as floating and emergent herbfields
and aquatic communities.
The coastal rivers of south-eastern Australia maintain
base flow throughout the year and support riparian
forests, scrub, sedgelands and grasslands, as well as
in-stream biota and floating and emergent herbfields.
Base flow plays a poorly defined role in maintaining
flows in inland river systems and is not considered to
be an important factor in determining the distribution
or composition of ecosystems (Hatton and Evans 1998).
Hatton and Evans (1998) noted that across at least some
of its range the platypus was an example of groundwater
dependent fauna. In some parts of this species’ range,
groundwater is required to sustain the flow or pools in
which it feeds.
Groundwater flux is likely to be the key attribute
influencing groundwater dependency. Sufficient
discharge of water is needed to maintain the level of
flow required by the various ecosystems. Groundwater
level in the riverine aquifer is also important in
terms of maintaining a hydraulic gradient towards the
stream that supports the necessary discharge flux.
Contamination of the riverine aquifers by nutrients,
pesticides and other toxicants may adversely affect
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dependent ecosystems in base flow streams. Aquatic
communities would be expected to be the worst affected.
2.2.5 Cave and aquifer ecosystems
This category comprises the aquatic ecosystems that may
be found in free water within cave systems and within
aquifers themselves. Gibert (1996) argued that aquifer
ecosystems represented the most extended array of
freshwater ecosystems across the entire planet.
Australia studies of these “stygean” ecosystems have
traditionally related to cave, rather than aquifer
systems, however there is a growing body of information
on the latter.
Spate and Thurgate (1998) noted that the karst
ecosystems of the Cape Range of Western Australia are
considered to be amongst the most diverse of their kind
in the world. Their subterranean fauna are considered
to be internationally significant. Karst and other cave
systems elsewhere also support diverse ecosystems (e.g.
Piccaninnie Ponds in South Australia; Scholz 1990).
Aquifers themselves support diverse array of
ecosystems. Their fauna largely consists of
invertebrates. Some ecosystems (e.g. in riverine
plains) exist along a continuum between fully aquatic
communities and fully aquifer communities (Danielopol
1989). Aquifer ecosystems are not necessarily confined
to near surface environments. The so-called stygofauna
(animals occupying in cave or aquifer habitats) have
been identified at depths of up to 600 m (Longley
1992).
The environment in which aquifer ecosystems develop is
characterised by darkness, consistency and persistence
of habitat and low energy and oxygen availability. The
organisms that inhabit these environments are often
specialised morphologically and physiologically. Their
stable and confined environment results in high levels
of endemism and high proportions of relictual species
compared with surface environments (Danielopol 1989).
Recent work in north-western Australia has identified
entire major lineages (orders or classes) of stygofauna
that are thought not to have been represented in
surface ecosystems since the Mesozoic era. Numerous
other major taxa that were previously unknown in
Australia have also been found (Humphreys 1999; Watts
and Humphreys 1999).
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Some aquifer systems are highly stratified, with each
layer supporting distinct communities of aquatic
organism (e.g. calcrete aquifers of central Western
Australia; Humphreys 1999).
Groundwater level, flux and quality are the three
attributes likely to be of greatest significance to
aquifer cave and aquifer ecosystems. Groundwater level
and flux will determine the amount of groundwater
available to support cave ecosystems. Where the
composition of aquifer ecosystems change with depth,
reductions in groundwater level may result in the loss
of particular species of communities of aquatic
organism.
In the stratified groundwaters of the calcrete aquifers
of central Western Australia, there are marked
differences in chemical composition between layers. Any
change in groundwater level might also result in marked
change in groundwater quality. Ecosystems in these
aquifers are highly specialised and may be lost
entirely with changes in groundwater level of only 1-2
m (Humphreys 1999).
Many aquifer ecosystems have developed in very stable
environments. Subtle changes in groundwater quality due
to contamination by (e.g.) agricultural chemicals or
septic tank effluent may result in changes in ecosystem
function. The potential sensitivity of aquifer
ecosystems to changes in groundwater quality raises the
prospect of their use as bio-indicators (Gibert 1996).
2.2.6 Terrestrial fauna
Descriptions of groundwater dependent ecosystems in the
previous sections have mainly concentrated on plant
communities. These communities provide habitat for a
variety of terrestrial, aquatic and marine animals,
which by extension must also be groundwater dependent.
However there is an additional group of groundwater
dependent fauna whose reliance on groundwater is not
based on the provision of habitat, but as a source of
drinking water. Groundwater, as river base flow or
discharge into a spring or pool, is an important source
of water across much of the country, particularly in
northern and inland Australia and other areas with
semi-arid climate. Its significance is greater for
larger mammals and birds, as many smaller animals can
obtain most of their water requirements from
respiration.
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Pastoralists in inland Australia have made extensive
use of groundwater to supply drinking water to grazing
stock. In addition to watering stock, groundwater is
also used by native fauna (e.g. kangaroos) and pest and
feral animals. Provision of water has allowed larger
populations of both wildlife and pest animals to be
sustained than would otherwise be the case.
Groundwater dependent terrestrial and riparian
vegetation and wetlands may be used by terrestrial
fauna as drought refuges. Access to groundwater allows
the vegetation to maintain its condition and normal
phenology (e.g. nectar production, new foliage
initiation, seeding). Populations of some birds and
mammals retreat to these areas during drought and then
recolonise drier parts of the landscape following
recovery. The long term survival of such animal
populations relies on maintaining the vegetation
communities and ensuring their water requirements are
met.
The key groundwater attributes will be flux, level or
pressure, depending on the hydrology of the system
providing the water.
2.3 Threatening processes
Like most other ecosystems, those dependent on
groundwater face a broad range of direct and indirect
anthropogenic threats. Threatening processes may act on
the ecosystem itself and/or on the groundwater and
other hydrologic processes upon which they in turn
depend. The main factors that threaten ecological
processes in groundwater dependent ecosystems in
Australia are described below.
2.3.1 Water resource development
Consumptive use of water resources pose a major threat
to groundwater dependent ecosystems in many landscapes
across Australia (and internationally). This is
particularly true in the more intensively developed
landscapes of eastern and south-western Australia, but
applies to some ecosystems in remote inland areas (e.g.
Great Artesian Basin mound springs). Consumptive uses
of groundwater and surface water resources potentially
impact on ecological processes in groundwater dependent
ecosystems.
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Consumptive use can impact on each of the four main
groundwater attributes, as follows:
Level or pressure – the most obvious impact of
consumptive use of groundwater is to lower the water
table level or reduce the pressure in a confined
aquifer. Potential impacts on dependent ecosystems
could include:
• reduced access to groundwater – groundwater level
may fall below the rooting depth of terrestrial
vegetation or the depth to which groundwater will
discharge directly to the surface (or to holes dug
by terrestrial fauna in groundwater soaks). The
environment for groundwater dependent ecosystems
may effectively dry out to the point where there is
a change in species composition or greater
vulnerability to other environmental stresses;
• reduced base flow in streams - this in turn may
reduce or eliminate habitat for in-stream aquatic
communities at certain times of year and result in
a shift in species composition or even collapse of
the ecosystem;
• loss of habitat - in cave and aquifer ecosystems,
where reduced groundwater levels may lead to the
loss of aquatic habitat at particular levels in the
cave system or aquifer and potentially the loss of
species dependent on that particular niche.
Diversion and/or impoundment of surface waters may
result in changes in the groundwater level,
particularly in near-stream alluvial aquifers.
Groundwater levels may increase if the postregulation stream flows exceed natural flows or they
may be lower, particularly if river regulation is
associated with out of basin transfers of water.
Elevated groundwater levels may advantage some
groundwater dependent species, whilst disadvantaging
those vulnerable (for example) to increased
waterlogging. Elevated groundwater levels (coupled
with changes in the nature of flooding) may
eventually result in excessive accumulation of salts
in the root zone of vegetation, the loss of sensitive
species and any dependent fauna (e.g. Jolly et al.
1993).
Flux – reduced potentiometric head accompanying
groundwater resource development may result in lower
hydraulic gradients towards groundwater discharge
areas and reduced discharge fluxes. The implications
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for some ecosystems will be similar to that for
reduced groundwater level or pressure. Reduced
discharge flux may lead to environmental decline in
estuarine or near shore marine ecosystems that rely
on the dilution effects of relatively fresh
groundwater to provide an appropriate habitat.
Quality – groundwater resource development has
potential to alter water quality, particularly within
the aquifer itself. Abstraction may lead to water
from other parts of an aquifer (or from nearby
surface water features or the ocean) being drawn
towards pumped zones. If water quality changes
substantially as the result of this, it may be to the
detriment of any aquifer ecosystem present.
2.3.2 Agricultural land use
Intensive agricultural land use is invariably
associated with changes in vegetation cover and
recharge-discharge relationships across catchments and
groundwater basins. The nature of these changes varies
with the physical character of the landscape (climate,
soils, topography, geomorphology, hydrogeology), the
degree of change in vegetation and the management of
agricultural land.
The introduction of dryland agriculture across much of
southern Australia has resulted in increased
groundwater recharge. This has in turn lead to
groundwater levels rising across landscapes and to an
enhancement of groundwater discharge at certain
topographic positions (e.g. breaks of topographic
slope, valley floors, streams; e.g. Coram 1999).
Dryland salinity and shallow water tables affect
millions of hectares of largely cleared agricultural
land throughout southern Australia (Agriculture Western
Australia et al. 1996; Murray Darling Basin Ministerial
Council 1999). Direct groundwater discharge into stream
channels and salt wash-off from affected land have also
contributed to enhanced salinity in tributary streams
and major rivers.
Fragmented remnant native vegetation in lower parts of
landscapes is particularly vulnerable to the effects of
shallow water tables and salinity. Recent reports from
WA (e.g. Hatton and Salama 1999) suggest that several
hundred indigenous plant species are at direct risk of
extinction due to dryland salinity.
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Irrigated agriculture is having similar impacts,
although not to the same areal extent. The application
of irrigation water has resulted in shallow water
tables across most irrigation districts and in some
surrounding unirrigated land. This has similar impacts
on native vegetation remnants to shallow water tables
in dryland areas. Disposal of saline drainage water
into streams and wetlands has also contributed to
elevated salt concentrations.
Many of the ecosystems threatened by irrigation and
dryland salinity are probably groundwater dependent.
Those ecosystems most affected generally occupy parts
of the landscape that were naturally (relatively) well
watered, by surface water, groundwater or both. Dryland
and irrigation salinity have changed two key
groundwater attributes that influence those ecosystems:
Level –the terrestrial, riparian and wetland
ecosystems that have been affected by dryland and
irrigation salinity would often have adapted to
groundwater levels that were either lower than they
have become or were periodically lower, such that the
root zones were not continuously waterlogged.
Increased evaporative discharge of the more elevated
water tables also results in an accumulation of salt
in the root zone (e.g. Jolly et al. 1993). This has
potential to compound the effects of shallow water
tables.
In terrestrial vegetation communities, it is often
the mature trees with deeper root systems that are
lost first. Recruitment may also be affected.
Ultimately the more waterlogging and salt sensitive
species are lost and the ecosystem may be invaded by
more tolerant species (e.g. Spiny Rush in southeastern Australia). Since these impacts generally
take place on fragmented native vegetation remnants
and may be expected to be concentrated in drought
refuges, dryland salinity may also have serious
consequences for fauna populations.
Continuously high water tables in wetlands as a
consequence of dryland and irrigation salinity may
bring about a change in water regime that does not
suit species or ecological processes requiring
periodic drying. As discussed above, it may also
result in salt concentrating in the soil profile.
Where water tables are particularly shallow and
groundwater highly saline, this may result in
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salinisation of the soil profile and collapse of the
natural ecosystem.
Elevated groundwater levels also result in increased
discharge of groundwater into streams and rivers.
Coupled with salt wash off from affected land, these
processes lead to enhanced stream salinities (MDBC
Ministerial Council 1999) and impacts on aquatic
ecosystems (that may or may not have been groundwater
dependent). The sensitivity of plant and animal
species and ecological processes in aquatic
ecosystems varies widely. Species diversity and
ecosystem complexity typically decline as salinity
increases.
Quality – rising groundwaters may mobilise salts
stored in the regolith and bring them towards the
surface. This factor and evaporative concentration
(when the water table is within 2-3 m of the surface;
Talsma 1963; Nulsen 1981) lead to increased
groundwater and soil solution salinities. The
consequences of this are described above.
Groundwater discharge into streams can lead to a
general increase in water salinity. It may also
result in the formation of saline pools in the floor
of streams. Deeper pools may act as refuges for
aquatic species during periods of low or no flow.
Under natural conditions they may have been feed by
relatively fresh groundwater derived from stream
flows. Hydrogeological changes accompanying
agricultural land use may result in more saline
(regional) groundwater discharging into these pools.
This may make them unsuitable habitats for all but
the most tolerant species. Flushing of these pools
during high flow events may also send a pulse of
saline water along the stream, which may affect
sensitive aquatic species.
Agricultural land use may affect groundwater dependent
ecosystems in ways that are unrelated to dryland or
irrigation salinity. Application of agricultural
chemicals (fertilisers, herbicides, insecticides) may
result in contamination of groundwaters. The
concentrated application of mobile forms of nitrogen in
stock urine patches may also foster groundwater
contamination, particularly where soils are well
drained (e.g Dillon et al. 1999).
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Groundwater contaminants are most likely to pose a
problem for ecosystems in wetlands, lakes or estuaries
fed by groundwater discharge. Nitrogen contamination of
groundwater may result in algal blooms that alter the
structure and composition of aquatic communities.
Environmentally stable pesticides or any harmful
residues may accumulate through the food chain and pose
a threat to higher order predatory birds and marine or
aquatic organisms.
Under natural conditions, aquifers provided stable
environments. Contamination with agricultural chemicals
has potential to substantially change the chemical
environment experienced by aquifer ecosystems. More
sensitive may be harmed directly by such changes. Other
species may be favoured by changes in nutrient
availability (for example) and may come to dominate the
community. Recruitment and other important ecological
processes may also be threatened.
Drainage of agricultural land in coastal areas may
activate acid sulphate soils and severely impact on
stream, estuarine and near shore marine ecosystems (see
section 2.3.3).
2.3.3 Acid sulphate soils
Acid sulphate soils are wetland soils and
unconsolidated sediments that contain iron sulphides.
Under the reducing conditions provided by permanent
groundwater, the iron sulphides are stable and the
soils weakly alkaline. However, when exposed to
atmospheric oxygen, the sulphides oxidise and in the
presence of water form sulphuric acid (Powell and Ahern
1997). This in turn may dissolve clays, release toxic
concentrations of aluminium, iron and other metals (NSW
EPA 1998). Acidified water and bioaccumulation of any
heavy metals that are released may kill or harm aquatic
organisms and impair ecosystem function (particularly
recruitment in more sensitive species. Iron
precipitates out of the acidified water and may smother
plants and the streambed. This would deprive some
components of the ecosystem of their habitat.
Conversion of iron sulphides to sulphuric acid also
makes soils acidic, impairing plant growth, and in
extreme cases, rendering it incapable of supporting
support plant life.
Acid sulphate soils are extensive along the eastern and
northern coastline of Australia, although they are also
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found in inland areas derived from marine sediments
(Powell and Ahern 1997).
Direct excavation during construction activities and
any lowering of water tables associated with shallow
groundwater resource development or drainage activities
may lead to the activation of acid sulphate soils.
Agricultural land use and residential, golf course and
marina development in coastal areas all have potential
to activate acid sulphate soils.
Groundwater dependent ecosystems affected by acid
sulphate soils will most commonly be those occupying
groundwater discharge areas in estuarine or coastal
environments, such as mangroves and sea grass beds and
associated vertebrate and invertebrate communities,
aquatic ecosystems in estuaries of base flow dependent
streams and coastal wetlands supplied by groundwater.
Activation of acid sulphate soils also has implication
for agricultural and non-groundwater dependent marine
systems.
2.3.4 Urban and commercial development
Urban and commercial development in Australia threatens
groundwater dependent ecosystems in several ways. They
have potential to influence the groundwater attributes
that govern ecosystem function and, through clearing,
drainage and land reclamation, directly displace the
ecosystems.
Impacts on groundwater attributes are described below:
Level – new urban or commercial developments are
often associated with an intensification groundwater
resource development, to support domestic garden,
recreational or industrial uses. This would normally
result in a lowering of groundwater levels and, if
bore fields were located close to groundwater
dependent ecosystems, some type of ecosystem impact.
The groundwater-fed wetlands and dependent
terrestrial ecosystems of the Swan Coastal Plain of
Western Australia have been affected in this way
(Water Authority of Western Australia 1992; Froend et
al. 1993). Changes in groundwater level led to a
contraction in wetlands and increased vulnerability
of dependent terrestrial vegetation to moisture
stress.
Drainage and the construction of canals and marinas
may also lower groundwater levels in coastal areas.
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Depending on the scale of the change in groundwater
level, this may lead to decline in dependent
wetlands, terrestrial and riparian vegetation. It may
also activate acid sulphate soils in susceptible
areas (see section 2.3.3) and degrade nearby
ecosystems.
Watering of domestic gardens and urban parkland,
discharge from septic tanks, leakage from sewerage
pipes and disposal of storm water may contribute to
elevated water table levels and the development of
dryland salinity in some urban areas. While the
impact of this would normally be confined to urban
and residential infrastructure, it has potential to
affect native vegetation remnants (terrestrial
vegetation, wetlands, riparian vegetation) within
urban areas. Higher levels and greater salt
concentration may also affect any aquifer ecosystems
present.
Flux – groundwater pumping associated with urban and
commercial development may also reduce discharge
fluxes in aquifers. Depending on the location of bore
fields and the hydrogeological setting, this could
reduce base flow into streams, water levels in
groundwater-fed wetlands and may result in more
saline conditions in near shore groundwater discharge
areas.
Analysis of the impacts of development of the Howard
East borefield to meet Darwin’s water requirements
found that it threatened to reduce discharge fluxes
in near shore marine environments which were
important crocodile breeding habitats (Sinclair
Knight Merz 2000). The change in discharge was
considered likely to make the environment more
saline, result in changed marine vegetation
composition and reduce breeding success for the
crocodiles.
Quality – urban development poses a particular threat
to groundwater quality. These may arise from (e.g.)
discharge of effluent from septic tanks, leakage from
underground fuel tanks, application of fertilisers
and pesticides to parks, gardens and recreation areas
and spills of industrial chemicals. Ecosystems may be
poisoned directly by pesticides and hazardous
chemicals or their ecological processes may be
disturbed by changes in nutrient availability and
consequences such as algal blooms and eutrophication.
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Impacts from these hazards are likely to be greatest
on aquatic ecosystems – in the aquifers themselves,
in wetlands and base flow dependent streams.
2.3.5 Mining
The direct impacts of mining on groundwater dependent
ecosystems will vary with the type of mining, the need
for and intensity of groundwater pumping and the
proximity to groundwater dependent ecosystems. Mining
related industrial activities (e.g. on-site processing)
and residential development may also affect groundwater
dependent ecosystems (see section 2.3.4).
Mining may affect each of the key groundwater
attributes, as described below.
Level or pressure – mine dewatering will lower the
water table level or aquifer pressure. The magnitude
and rapidity of change will be relatively great for
large open cut mines or where the mine intersects
highly transmissive aquifers (e.g. deep leads). Minerelated construction activities, such as diversion
and/or canalisation of streams, may also contribute
to changes in riverine aquifer levels.
Impacts on groundwater dependent ecosystems in
proximity to the mine could be substantial. Lowering
of water table levels could reduce or even eliminate
cave or aquifer ecosystems that used the groundwater
as habitat and were situated in close proximity to
the mine. Mine dewatering impacts are unlikely to
have a major impact on base flow dependent systems,
unless the mine was located close to a spring that
was the main source of flow or there were a cluster
of mining operations that produced a more regional
scale change in groundwater levels. Wetlands and
groundwater dependent terrestrial or riparian
ecosystems may be threatened by large changes in
groundwater level or pressure.
Tailings dams associated with mining operations may
contribute to a local elevation in groundwater levels
if they leak and/or are in hydraulic connection with
aquifers. Impacts on any nearby groundwater dependent
ecosystems would be similar to those of dryland
salinity (see section 2.3.2)
Flux – mine dewatering also has potential to reduce
discharge flux and volumes of water available for
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habitat for aquatic ecosystems in wetlands and base
flow streams.
Quality – mining poses several hazards to groundwater
quality. Where groundwater is stratified or changes
in quality (e.g. salinity, pH, chemical composition)
with depth, dewatering may alter the environment
experienced by (affected) cave or aquifer ecosystems.
Ecosystems sensitive to those changes may be
simplified or even eliminated by such changes.
Solution mining (e.g. for gold or uranium) using
toxic chemicals like cyanide may completely destroy
any aquifer ecosystem present. Accidental spillage
from tailings dams may contaminate surface water and
groundwater systems and damage the ecosystems they
support.
Subsidence associated with large scale mine dewatering
may indirectly affect groundwater dependent ecosystems.
Subsidence could affect surface water flow processes in
streams and adjacent riverine aquifers. In coastal
areas, it could increase the risk of seawater intrusion
into groundwater dependent coastal wetlands.
2.3.6 Plantation forestry
Plantation forestry development, like agricultural
development, results in changes in vegetation cover and
hydrologic processes. Unlike agricultural development,
it generally results in increased evaporation and
reduced run-off, stream flow and groundwater recharge
(Zhang et al. 1999).
Most early forestry plantations in Australia were
established by clearing native forests and woodlands.
The recent rapid expansion in plantation area is almost
exclusively based on the reafforestation of former
agricultural land. Changes in surface water flows and
groundwater recharge would be expected to be greater in
the latter case. However it is unclear under which
scenario the impacts on any groundwater dependent
ecosystems would be greater.
The main impact of plantation forestry development
would be to reduce the level or pressure of groundwater
(depending on whether the aquifer was confined or
unconfined). This would arise from two processes.
Reduced recharge to the aquifer below the plantation
would directly result in a lowering of the water table
or a reduction in pressure. Reduced surface water flows
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from reafforested catchments may also reduce recharge
to riverine aquifers.
Impacts of plantation forestry depend on the scale of
reafforestation in relation to the catchment and
groundwater basin of concern and the respective
contribution of these areas to the water resources of
the catchment or basin as a whole. Conversion of whole
or large proportions of catchments has been shown to
lower groundwater levels (e.g. Linke et al. 1995). This
may be beneficial to natural ecosystems if they had
been artificially elevated under agricultural land use
(see section 2.3.2). However, the lowering of water
tables or aquifer pressure may ultimately disrupt
ecological processes in any groundwater dependent
ecosystems present.
Where only a small proportion of the catchment is
reafforested, the net impact may be relatively low. The
exception to this would be in large basins or
catchments where relatively extensive plantation
development takes place in the higher rainfall areas
where the majority of the recharge and surface flows
are generated. Plantation development in these areas
may reduce the level or pressure of important aquifers
and may substantially reduce stream flow.
Surface water flows generated in the wetter parts of
the catchment are likely to be fresher (less salty)
than those generated in drier areas. Reduction in
fresher surface water flows may lead to a deterioration
in water quality in the lower part of a river basin.
This may in turn impact on surface water and
groundwater dependent ecosystems.
Lowering of levels (or pressure) in groundwater basins
where there is already considerable consumptive use
will place further stress on the aquifer and on any
groundwater dependent ecosystems. This is particularly
true where no specific environmental water provision
for dependent ecosystems has been made (see section 4)
or where groundwater allocation is based on the former
water regime, where there was largely agricultural land
use.
2.4 Important groundwater dependent ecosystems
Table 2.1 contains an assessment of the relative
importance of the major Australian groundwater
dependent ecosystems. The list of dependent ecosystems
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has largely been drawn from that of Hatton and Evans
(1998) and does not represent an exhaustive list of the
nation’s groundwater dependent ecosystems. The most
likely threats to ecological function in these
ecosystems have been described (from section 2.3), as
have the groundwater attributes most likely to be
affected by the threatening process. Importance is
based on an environmental risk analysis of the key
threats to ecosystem health. Three factors are
considered:
risk – the likelihood of a threat to ecosystem
function being realised
vulnerability – the severity of decline in ecosystem
health or function if a threat was realised;
value – the conservation value or uniqueness of an
ecosystem.
Each factor was scored from 1 (low) to 3 (high).
Importance ratings (low-high) were based on the product
of risk, vulnerability and value ratings.
Ecosystems that are entirely dependent on groundwater
tended to receive higher importance ratings than other
ecosystems. Their high level of dependency on
groundwater makes them vulnerable to change in water
regime. Many of these ecosystems were also assigned a
high conservation value rating in acknowledgment of the
relatively high levels of endemism reported.
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Table 2.1: Relative importance of some Australian
groundwater ecosystems
Threat to ecosystem
Ecosystem
Process
Vulnerabi
Risk
Value
Importanc
lity
e
Groundwat Impact if Likelihoo Conservat
Risk ×
er
threat
d of
ion value Vulnerabi
attribute realised
threat
of
lity ×
being
ecosystem
value
realised
Entirely dependent on groundwater
•
Mound spring ecosystems
Water resource
Pressure
High
High
High
High
•
Karstic groundwater ecosystems
Level,
quality
High
High
High
High
•
Permanent lakes and wetlands
of Swan Coastal Plain
Level,
quality
High
High
Moderate
High
•
Pilbara spring ecosystems
Level,
quality
High
Moderate
High
High
•
Inland mangrove near 80 Mile
Beach in Western Australia
Arid zone groundwater calcrete
ecosystems
Riverine aquifer ecosystems
Water resource,
agriculture,
mining
Urban &
commercial,
water resources
Mining, water
resource,
agriculture
No immediate
threat
Water resource,
mining
Water resource,
agriculture,
urban &
commercial
development
Water resource,
mining
Level
High
Low
High
High
Level,
quality
Level,
quality
High
Moderate
High
High
High
High
Moderate
High
Level,
quality
High
Moderate
High
High
Water resource,
mining,
agriculture
Urban &
commercial,
water resource
Water resource,
agriculture,
forestry
Water resource,
urban &
commercial
Water resource
Level,
quality
High
Moderate
Moderate
High
Level,
quality
High
Moderate
High
High
Level,
quality
Moderate
High
Moderate
High
Level,
quality
High
High
Moderate
High
Level,
flux
Level,
quality
High
Low
Moderate
Moderate
High
Low
Moderate
Moderate
Water resource, Level,
agriculture
quality
High
Low
Moderate
Moderate
Agriculture
High
Low
Moderate
Moderate
Moderate
Moderate
Moderate
Moderate
Moderate
Moderate
Moderate
Moderate
•
•
•
Marine tide influenced cave
(or anchialine) ecosystems
Highly dependent on groundwater
•
Pilbara river pool ecosystems
•
Near shore stromatolites of
coastal Western Australia
•
Groundwater dependent wetlands
of basalt plains of Western
Victoria
Damplands of Swan Coastal
Plain
•
•
•
•
•
•
•
Mesophyll palm vine forests of
tropical north Australia
Solution hollow swamp
communities of Eyre and Yorke
Peninsulas
Permanent water hole
ecosystems of rivers and lakes
of Central Australian lowlands
and South Australian ranges
Melaleuca stands in upper
south-east of South Australia
Paperbark swamp forests and
woodlands of tropical northern
Australia
Base flow dependent aquatic
ecosystems of uplands of
south-eastern Australia
Agriculture
Water resource
Level,
quality
Level
Water resource, Level,
agriculture
flux,
quality
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Threat to ecosystem
Ecosystem
Process
Vulnerabi
Risk
Value
Importanc
lity
e
Groundwat Impact if Likelihoo Conservat
Risk ×
er
threat
d of
ion value Vulnerabi
attribute realised
threat
of
lity ×
being
ecosystem
value
realised
Proportionally dependent
ecosystems
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
Permanent coastal lake, dune
and beachridge plain
ecosystems of coastal NSW and
coastal sand islands of NSW
and Qld.
Phragmites and Typha
communities of permanently
flooded swamps and lakes of
inland areas of the uplands of
south-eastern Australia
Permanent base flow dependent
swamps and river pools of
Kangaroo Island
Riparian swampland communities
of Mount Lofty Ranges
Swan Coastal Plain damplands
and sumplands with paperbark
and Banksia woodlands
Coastal swamp scrub sedgeland
communities in the nearcoastal dune systems of the
Upper South East of South
Australia
Base flow dependent ecosystems
in south-western Western
Australia
Lake and riparian sedgelands,
swamp heaths and bog
communities in Tasmania
Groundwater dependent
seasonally-permanently
waterlogged swamp heathlands,
sedgelands, and Phragmites
grasslands in Tasmania, where
waterlogging is dependent on
groundwater levels
River pool and billabong
herblands of floodplains in
tropical northern Australia
Base flow dependent herbland
ecosystems of uplands and
plateaux of northern Australia
Lake ecosystems of major river
systems of north-eastern
Australia
Volcanic crater lakes and
swamps of Cape York Peninsula
Permanent glacial lakes
supporting wet tussock and
Carex grasslands and Sphagnum
swamps in the south-eastern
uplands
Swamp heaths and sclerophyll
forests of the Hawkesbury
Urban &
commercial,
water resource,
acid sulphate
soils
Water resource,
agriculture
Level,
quality
High
High
Moderate
High
Level,
quality
High
High
Moderate
High
Water resource, Level,
agriculture
quality,
Flux
Water resource, Level,
agriculture
quality
Water
Level,
resources,
quality
urban &
commercial
Agriculture
Level
Moderate
High
Moderate
High
Moderate
High
Moderate
High
High
High
Moderate
High
High
Moderate
Moderate
High
Water
Level,
resources,
quality
agriculture,
forestry
Agriculture,
Level
water resources
Moderate
Moderate
Moderate
Moderate
Moderate
Low
Moderate
Moderate
Agriculture,
Level,
water
quality
resources,
forestry, urban
& commercial
Moderate
Moderate
Moderate
Moderate
Mining,
agriculture
Level,
quality
Moderate
Low
Moderate
Moderate
Mining,
agriculture
Level,
flux
Moderate
Low
Moderate
Moderate
Agriculture
Level,
flux
Moderate
Low
Moderate
Moderate
Agriculture,
water resource
No immediate
threat
Level,
quality
Level
Moderate
Low
High
Moderate
High
Low
Moderate
Moderate
Moderate
Moderate
Moderate
Moderate
Water resource, Level
agriculture,
urban &
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•
•
•
•
•
Sandstones and inland
floodplains of the uplands of
south-eastern Australia
Eleocharis and Baumea
sedgelands in lagoons of the
inland rivers of the southeastern Australia
Alpine bogs in the highlands
of NSW and Victoria
Ecosystems fringing the
Gippsland Lakes in eastern
Victoria
River plain grasslands on the
floodplains of the North
Australian Plateau
Tropical sclerophyll forests
and woodlands on the North
Australian Plateau
commercial
Water resource, Level
agriculture
Moderate
Moderate
Moderate
Moderate
No immediate
threat
Agriculture,
urban &
commercial
Mining,
agriculture
Level
Moderate
Low
Moderate
Moderate
Level,
quality
Moderate
Moderate
Moderate
Moderate
Level,
flux
Low
Low
Low
Low
Low
Low
Low
Low
Water resource, Level
agriculture
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Threat to ecosystem
Ecosystem
Process
Vulnerabi
Risk
Value
Importanc
lity
e
Groundwat Impact if Likelihoo Conservat
Risk ×
er
threat
d of
ion value Vulnerabi
attribute realised
threat
of
lity ×
being
ecosystem
value
realised
Ecosystems with opportunistic
groundwater dependence
•
Ecosystems of the Coorong
•
Ecosystems of permanent lakes
and swamps at termini of
inland rivers in the Central
Lowlands and South Australian
Ranges
Major ocean embayments such as
Port Phillip Bay
•
•
•
•
•
•
Intermittent floodplain lakes
of the Central Lowlands
Swamp sclerophyll forests on
the coastal floodplains of the
uplands of south-eastern
Australia, and of the LanderBarkly Tablelands
Jarrah forest and Banksia
woodlands of south-western WA
Lignum shrublands on inland
river systems
Coastal mangrove and salt
marsh ecosystems
Agriculture,
Level,
water resources quality
Agriculture,
Level
water resource
Moderate
High
High
High
High
Moderate
Moderate
High
Agriculture,
urban &
commercial,
acid sulphate
soils
Agriculture,
water resource
Agriculture
Flux,
level,
quality
Moderate
High
Moderate
High
Level,
quality
Level
Moderate
Moderate
Moderate
Moderate
Moderate
Moderate
Moderate
Moderate
Agriculture
Level
Moderate
Moderate
Low
Moderate
Agriculture,
water resource
Agriculture,
urban &
commercial,
acid sulphate
soils
Level
Moderate
Moderate
Low
Moderate
Level,
quality
Moderate
High
Low
Moderate
N.B. Importance rating is based on the sum of vulnerability, risk and value
ratings. If total score < 4 – low rating, if score is between 4 and 8 –
moderate rating; if score is >8 high rating. High, moderate and low equate
to scores of 3, 2 and 1, respectively, for vulnerability, risk and value
ratings.
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3. Environmental Water Requirements of Groundwater
Dependent Ecosystems
3.1 Introduction
If groundwater policy and management systems are to
appropriately consider groundwater dependent ecosystems
they will need to be informed by:
an understanding of the nature of that dependency;
the water requirements of the ecosystem;
the groundwater regime required to meet the water
requirements of the ecosystem;
the impacts of change in key groundwater attributes
on that ecosystem.
Figure 3.1 outlines a conceptual framework for a
process by which these information requirements may be
met and, in effect, the environmental water
requirements of groundwater dependent ecosystems
determined. The remainder of this section describes the
four key components of the framework, namely:
identification of potentially groundwater dependent
ecosystems;
analysis of ecosystem dependency on groundwater;
assessment of water regime in which dependency
operates;
environmental water requirement determination
Section 4 outlines a second conceptual framework by
which this (and other) information can incorporated
into a groundwater allocation process that would set
environmental water provisions for groundwater
dependent ecosystems.
3.2 Identifying potentially groundwater dependent
ecosystems
The first step in any process of allocating groundwater
to meet the environmental needs of dependent ecosystems
is to actually identify those ecosystems. A two step
process is depicted in Figure 3.1, the identification
of potentially dependent systems and a more detailed
analysis of the nature of that dependency.
Potentially groundwater
initially identified in
based on rapid desk top
field analyses. The use
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several ways. Approaches may be
or relatively straightforward
of any particular approach
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would depend on the nature of the potential groundwater
dependency, as well as data and resource availability.
Several approaches are outlined below.
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Figure 3.1: Conceptual framework for determination of environmental water
requirements of groundwater dependent ecosystems
Ecology –
recruitment, fire,
Habit
Consumptive
use -
Increased
Reduced
Identify
groundwater
dependent elements
of ecosystem
Flux
Potentially
groundwater
dependent
Determine processes
or uses for which
water is required
Proportional
response
Press
Timing,
frequency,
Identify key
groundwater
attributes
Level
Smaller
Rate of
Key ecological
processes
Determine pattern
of water usage
Range in
level,
Quali
Determine extent or
type of dependency
Response to change
Consistency
of
/
Environmental water
requirement
Target level of
ecosystem health
Threshold response
Identify sources of
water ecosystem
exploits
Minor impact
Simplified
Ecosystem
Entir
Surface
Highl
Proportio
Opportuni
Dependency Analysis
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Rain & soil
Assessment of water regime in which
d
d
t
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d t
i ti
36
Observing the importance of groundwater to the
ecosystem - the groundwater dependency of many
ecosystems is self-evident. Examples include aquatic
ecosystems whose habitat is groundwater (e.g. cave
and aquifer ecosystems) or groundwater derived (base
flow dependent ecosystems) of such ecosystems include
those for which groundwater is the habitat or is the
major part of it (e.g. cave and aquifer ecosystems)
or for which groundwater is clearly the sole source
of water over at least a prolonged dry period (e.g.
aquatic ecosystems in base flow streams, mound
springs). Potential dependency of ecosystems with a
less stringent reliance on groundwater would need to
be identified in other ways.
Desk top appraisal - PPK (1999) outlined a desk top
appraisal approach to assessing potential groundwater
dependency. A brief checklist was prepared that
helped to indicate groundwater dependency based on
correlation with the ecology, location and/or
function of an ecosystem. This approach has been
extended in Table 3.1 to provide a checklist that
could be used to infer groundwater dependency for
terrestrial, marine and/or aquatic ecosystems where
there were multiple positive responses.
Table 3.1:
Groundwater dependency assessment checklist
Ecosystem traits that imply groundwater dependency
Yes
No
Is the ecosystem identical or similar to another that is
known to be groundwater dependent?
Is the distribution of the ecosystem associated with surface
water bodies that are or are likely to be groundwater
dependent? (e.g. permanent wetlands, streams with consistent
or increasing flow along the flow path during extended dry
periods)
Is the distribution of the ecosystem consistently associated
with known areas of groundwater discharge? (e.g. springs or
groundwater seeps in terrestrial and/or near shore marine
environments)
Is the distribution of the ecosystem typically confined to
locations where groundwater is known or expected to be
shallow? (e.g. topographically low areas, major breaks of
topographic slope)
Does the ecosystem withstand prolonged dry conditions
without obvious signs of water stress?
Is the vegetation community known to function as a refuge
for more mobile fauna during times of drought?
Does the vegetation in a particular community support
greater leaf area index and more diverse structure than that
in nearby areas in somewhat different positions in the
landscape?
Does expert opinion indicate that the ecosystem is
groundwater dependent?
a
a
a
a
a
a
a
a
a
a
a
a
a
a
a
a
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Leaf area index estimation - there is considerable
evidence (see Hatton et al. 1996) that leaf area
index (LAI) of plant communities is a strong
indicator of water availability in semi-arid to arid
environments. In such environments vegetation that
consistently and perhaps even opportunistically
exploited groundwater would be expected to have
greater LAI than those that were entirely rainfed.
Various measures have been used to make comparisons
between expected and actual LAI. Indices of
vegetation greenness have been developed to provide
spatial estimates of LAI, generally using remotelysensed images. Differences in the relative value of
these indices from such images could be used to
identify and map potentially dependent ecosystems
(McVicar et al. 1994).
Specht (1972) developed empirical relationships
between climate indices and LAI. Comparison of
expected LAI values on the basis of such indices with
that of local vegetation would provide some
indication of groundwater dependence.
Use of LAI as an indicator of water availability
relies on the vegetation being in equilibrium with
climate and groundwater availability. Assessments of
LAI should not be made immediately after the plant
communities have been disturbed (e.g. by fire, insect
attack or logging).
Indications from plant water relations physiological measurements of plant water relations
may provide an indication of potential groundwater
dependency.
Pre-dawn leaf water potential provides a good
indication of the difficulty plants are experiencing
in extracting water from the soil profile, with
greater leaf water potential indicating (other
factors being equal) reduced water availability.
Plants with lower values of leaf water potential than
would be expected on the basis of antecedent climate,
soil water availability and/or comparison with nearby
vegetation could indicate groundwater uptake (e.g.
Clifton and Miles 1998).
Leaf porometry (e.g. McJannet et al. 2000) may also
be used to infer water availability to plants.
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Relatively high values of stomatal conductance and
leaf transpiration during a prolonged period of
severe soil water deficit suggests some groundwater
uptake.
Bore hydrograph interpretation - diurnal logging of
groundwater level can be used to identify potentially
dependent ecosystems. Farrington et al. (1990) and
Salama et al. (1994) both detected small changes in
groundwater level that were independent of diurnal
fluctuation in barometric pressure. These were
considered to be due to plant water uptake and
therefore suggest groundwater dependency.
3.3 Dependency analysis
The second step defined in Figure 3.1 in determining
the environmental water requirements of groundwater
dependent ecosystems is “dependency analysis”. This
step provides a qualitative assessment or description
of the nature of ecosystem dependence on groundwater.
The process would provide more conclusive evidence that
potentially dependent ecosystems (section 3.2) were
actually groundwater dependent.
By defining the groundwater dependent elements of the
ecosystem and describing the nature of their
dependency, the analysis would help to target any
investigations needed to determine the specific
environmental water requirements of the ecosystem.
Dependency analysis should not be a resource intensive
activity. Providing there was adequate published
information about the ecosystem, it could be largely
performed as a desk top study.
The three components of dependency analysis are
described below:
Identification of groundwater dependent elements of
the ecosystem - groundwater dependent elements of the
ecosystem could include plants and animals, as well
as ecological processes that support these organisms
and any geomorphological and/or hydrogeological
processes that help to maintain the aquifer.
This step is more applicable to potentially dependent
ecosystems in which only some members or processes
are likely to be directly dependent on groundwater.
This group might include terrestrial vegetation and
some marine systems, in which only certain dominant
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plant species are actually directly dependent.
Groundwater dependency of the various elements of
these ecosystems could be inferred using one or more
of the approaches outlined in section 3.2,
particularly appraisal of the extent to which traits
commonly associated with groundwater dependency are
displayed (e.g. vegetation LAI estimation and
assessment of plant water relations).
Comparison of plant rooting depths with groundwater
level may be sufficient to indicate groundwater
dependency in ecosystems where only the (terrestrial
or riparian) vegetation are likely to be dependent.
Identification of biophysical processes that are
potentially groundwater dependent would follow a
similar checklist approach to that described for
ecosystems in Table 3.1. The approach would require
that the main processes that influence the
distribution and function of the ecosystem be listed
and/or described and an assessment made of the likely
dependency on groundwater. Processes that should be
considered would include recruitment and succession,
persistence, water, salt and nutrient balance and
carbon or energy balance.
In cases where the majority of the ecosystem is
directly dependent on groundwater (e.g. mound springs
ecosystems and aquatic ecosystems in base flow
dependent streams, groundwater lakes and aquifers),
it would not be necessary to identify all of the
likely directly dependent species. However, it may be
appropriate for later analyses to select indicator
species whose environmental water requirements would
be assessed. Selection of indicator species would be
based on their sensitivity to changes in groundwater
regime.
Identification of key groundwater attributes Environmental water requirements of groundwater
dependent ecosystems should be specified in terms of
four basic groundwater attributes (flux, level,
pressure, quality: Table 3.2). Determination of the
environmental water requirement requires an
understanding of the interaction between these
attributes and the dependent elements of a particular
ecosystem and of the way in which this varies with
time.
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Table 3.2:
Definition of key groundwater attributes
Attribute
Definition & description
Flux
Groundwater flux (flow) is the rate of surface or subsurface
discharge of an aquifer. It is relevant to the provision of
an adequate quantity of water to sustain an ecosystem per se
or of a sufficient quantity to dilute more saline water (in
estuarine, marine or wetland systems) to allow an ecosystem
to function. The former case applies to ecosystems that
occupy discharged groundwater (e.g. cave systems, aquatic
ecosystems in base flow dependent streams and many
groundwater-fed wetlands) or whose sole or principal source
of water is groundwater (e.g. mound springs).
Groundwater level is the depth of the water table. It is
relevant to a broad range of ecosystems including wetlands
fed by unconfined aquifers, terrestrial vegetation, many
coastal lake and estuarine ecosystems, some cave and aquifer
ecosystems and base flow dependent ecosystems. The
ecosystems’ occupation or usage of groundwater depends on the
water table level (above or below the surface) remaining
within a certain range.
Pressure has a similar role in ecosystems fed by confined
aquifers to that of level in systems fed by unconfined
systems. It applies, for example, to Great Artesian Basin
mound springs.
Groundwater quality is typical measured in terms of
electrical conductivity (or salinity), nutrient content
and/or contaminant concentrations (e.g. heavy metals,
pesticides). Ecosystems and their component species would
typically function adequately over certain ranges in water
quality. Outside these ranges, the composition and health of
the ecosystem is likely to decline. This groundwater
attribute becomes important to ecosystems in circumstances
where there is a sustained change in quality or trend away
from the natural water quality state.
Level
Pressure
Quality
The key groundwater attributes that most influence
dependent or potentially dependent ecosystem are
determined from an assessment of the way in which the
ecosystem relies on or uses groundwater. Several
groundwater attributes will be important in most
cases. Table 3.2 provides a framework for the
assessment process by indicating the scenarios in
which particular groundwater attributes are important
to ecosystems.
Determination of the type of groundwater dependency Hatton and Evans (1998) recognised five classes of
ecosystem dependency on groundwater. They were
described in detail in section 2.1 and have been
reiterated in Table 3.3. They serve a useful purpose
in highlighting the importance of groundwater to
ecological processes and the nature of ecosystem
response to changes in the key groundwater
properties.
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Table 3.3: Forms of ecosystem dependency on
groundwater (after Hatton and Evans 1998)
Type
Entirely
dependent:
Highly dependent:
Proportional
dependence:
Limited or
opportunistic
dependence:
No apparent
dependency:
Definition
Communities where only slight changes in key
groundwater attributes below or above a threshold would
result in their demise;
Communities where moderate changes in groundwater
discharge or water tables would result in a substantial
change in their distribution, composition and/or
health;
Communities that exhibit subdued, proportional
responses to changes in groundwater attributes;
Groundwater appears only to play a significant role in
the water balance of such ecosystems at the end of a
dry season or during extreme drought;
Communities that appear to be entirely rainfed or
dependent on surface water.
The classes of Hatton and Evans (1998) could
understate the long-term dependency of ecosystems on
groundwater, particularly for ecosystems with limited
or opportunistic dependence. The long-term
persistence of such ecosystems may entirely depend on
access to groundwater during crucial climatic events,
such as prolonged drought.
Allocating ecosystems into dependency classes would
again be based on an assessment of the
characteristics of the ecosystem and of the way in
which it uses or requires groundwater.
3.4 Assessment of current or natural water regime
This step is designed to provide a comprehensive
understanding of the water regime in which the
ecosystem in question operates. It has three components
(Figure 3.1 and following sections) and includes both
quantitative and qualitative elements. A greater level
of understanding and information is required than was
the case for the dependency analysis, particularly in
determining the pattern of water usage.
The water regime that would be assessed in most cases
would be that currently operating. While this may
adequately reflect the natural regime, it may, in some
circumstances differ markedly and not be capable of
sustaining the ecosystem in the long term. In such
cases the natural water regime may need to be inferred
or modelled from the current water regime and known
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changes in land use or management and ecological and/or
hydrogeological processes.
3.4.1 Determining the processes or uses for which water
is required
This step is a descriptive one and builds on the
understanding of groundwater – ecosystem interaction
gained by the dependency analysis (section 3.3).
Understanding the processes or uses that ecosystems
make of groundwater helps to guide the approach that
might be followed in the more quantitative step where
patterns of water usage are determined.
Requirements of ecosystems for groundwater can be
grouped into a few simple categories, as follows:
Consumptive use – whereby plants take up and
transpire groundwater to help meet evaporative demand
and physiological function or animals drink water
derived from groundwater to meet their water needs.
Habitat – whereby aquatic ecosystems occupy
discharged groundwater or aquifer ecosystems occupy
groundwater in situ.
Biophysical process – where groundwater plays a role
in sustaining important ecological or physical
processes, including:
• recruitment and succession – this could be either a
direct influence (e.g. requirement for certain
water regime to provide a suitable environment for
regeneration or reproduction) or an indirect one on
processes which in turn influence recruitment or
succession (e.g. prolonged lowering of water level
may increase the opportunity for fire, which would
in turn result in successional change in vegetation
composition);
• salt balance – where particular groundwater and
surface water regimes (groundwater level, frequency
of flooding events) are required to maintain soil
salinity levels within an acceptable range for a
particular vegetation community;
• nutrient balance – where groundwater is the main
source of nutrients (carbon and/or minerals) for
heterotrophic aquifer or cave ecosystems;
• geomorphological processes – where groundwater is
required to create or maintain physical habitats
such as caves or mound springs.
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3.4.2 Sources of water exploited by ecosystems
Groundwater may not be the sole source of water
exploited by many dependent ecosystems. Assessing the
environmental water requirements of such ecosystems
must recognise the respective contributions of surface
water, rainfall and soil water to the regime that
sustains the ecosystem.
Separating the contributions of each source may not be
a simple process, but is required to adequately define
the environmental water requirement. The first step in
this process would be to quickly consider the sources
of water and rate their respective contributions to the
water requirement. Potential approaches to quantifying
these components are the subject of the section 3.4.3.
It should be noted that the focus of this section is on
groundwater requirements. Arthington and Zalucki (1998)
contain reviews of a range of methods that have been
used to determine water requirements for surface water
systems.
3.4.3 Patterns of water usage
Patterns of water usage or water requirement by
dependent ecosystems have three dimensions:
thresholds – within which one or more of the four key
groundwater attributes must remain for the ecosystem
to be maintained;
rates of use – that indicate the consumptive use
and/or requirements of dependent ecosystems;
temporal distribution of use – patterns of water
usage or requirement will not be static over time for
many ecosystems. The temporal dimensions of usage –
timing, frequency, duration, episodicity – must all
be described to adequately determine the
environmental water requirement.
As discussed in section 3.3, determination of water
usage patterns may apply to ecosystems generally,
indicator species or to the dependent elements of
ecosystems that are only proportionally or
opportunistically dependent.
This section outlines approaches by which the three
dimensions of the water regime of dependent ecosystems
may be understood.
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3.4.3.1 Threshold values for groundwater attributes
Threshold values for groundwater flux, level, pressure
and/or quality would be assessed to determine the range
in these attributes over which the ecosystem or its
groundwater dependent elements are sustained. Several
approaches may be taken to this assessment:
Interpretation of monitoring – where groundwater
monitoring data was available, it would be reviewed
to determine the range in the relevant groundwater
attribute(s) which have so far sustained the
ecosystem. The purpose of the review would be to
identify the typical values and naturally occurring
extremes in groundwater level, pressure and/or
quality that have been recorded. The range in values
between the “typical” and extreme would provide a
“first cut” assessment of thresholds for those
attributes.
Such an approach may be unreliable in circumstances
where there has been considerable disturbance to the
hydrologic balance of the ecosystem. Natural extremes
in groundwater attributes may have been magnified by
recent human activities (e.g. abstraction might
exacerbate lowering of groundwater levels during
drought), without current ecosystem condition fully
reflecting the impact of these changes.
Periodic monitoring of both groundwater status and
environmental condition would provide a more
reliable indication of ecosystem groundwater
thresholds. Comparison of the two data sets might
indicate groundwater “events” that were implicated in
sudden changes in ecosystem condition or points or
events where there was a rapid shift in the trend in
ecosystem condition. New monitoring of this type
would be an important part of an adaptive management
system for ecosystems for which an environmental
water provision has been made (see section 4.3).
Expert assessment – in the absence of monitoring
information, it may be necessary to have relevant
experts offer opinions on the threshold in
groundwater flux, level, pressure or quality that
might result in the rapid collapse of the ecosystem
concerned. Thresholds might be interpreted from
understanding of the distribution of the ecosystem
and/or the groundwater conditions (especially level
or pressure) required for interaction with the
ecosystem.
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Examples where expert opinion might be applied
include:
• interpretation of the maximum root depth of
dependent terrestrial vegetation suggests a level
above which groundwater must rise to ensure
dependent elements of the ecosystem remain viable;
• interpretation of the level or pressure required to
enable surface discharge of groundwater which would
in turn provide necessary habitat for aquatic
ecosystems (e.g. base flow dependent systems) or
water for consumption by terrestrial fauna (e.g.
kangaroos dependent on groundwater soaks in the
arid zone).
Benchmarking against similar ecosystems – groundwater
conditions associated with either the collapse of
similar ecosystems or with those ecosystems in
various degrees of decline may be interpreted to
predict threshold values. Observations on multiple
examples of the same type of ecosystem may be used to
define a response function between the groundwater
attribute and ecosystem condition.
Base flow analysis - base flow analysis provides an
indication of the extent to which stream flows are
dependent on groundwater. Nathan and McMahon (1990)
describe analytical techniques that may be used to
derive base flow indices. The application of such
analyses in this case would be in determining the
times of year when base flow formed the sole or major
source of water in a stream and the discharge flux
required to sustain the required level of base flow.
This would indicate the threshold groundwater
condition, particularly for aquatic ecosystems
dependent on base flow to maintain their habitat
during dry seasons.
3.4.3.2 Rates of use
The environmental water requirement of ecosystems whose
main requirement of groundwater is for consumptive use,
should be closely correlated with the rate of
groundwater use. Consumptive use by other ecosystems,
particularly those that occupy groundwater (e.g.
wetland, stream, cave or aquifer ecosystems), may bear
little relation to the environmental water requirement.
Consumptive use of groundwater will often be only part
of the overall consumptive water use of the ecosystem
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or its dependent elements. Unless there is a clear
temporal demarcation between use of groundwater and
that derived from non-groundwater sources, methods will
need to be capable of discriminating between the
various sources of water (as discussed in section
3.4.2). Several approaches are outlined below. These
may be used separately and/or in combination with other
methods.
Measurement of plant water uptake – almost all water
taken up by (non-aquatic) plants is used to meet
atmospheric evaporative demand. Numerous
methodologies and instruments have been developed to
measure evaporation from individual plants and/or
vegetated surfaces (see Greenwood 1986). Their
application in environmental water requirement
assessments varies with the vegetation community
concerned, the nature of its groundwater dependency
and local surface topography:
• Eddy correlation, Bowen ratio techniques – these
techniques are only applicable in flat to gently
sloping landscapes with relatively large contiguous
areas (several hectares) of uniform vegetation.
Although they are theoretically the most accurate
methods for measuring evaporation, their
application would be limited in environmental water
requirement studies due either to their
requirements for topographic or vegetation
uniformity. They would not be appropriate for
vegetation communities in which only some elements
are groundwater dependent or for those in which the
groundwater dependent ecosystem comprises isolated
patches in otherwise entirely rainfed vegetation;
• Sap flow techniques – transpiration by woody
vegetation (trees and larger shrubs) is calculated
from measurements of water flow through the sapwood
(e.g. Edwards and Warwick 1984; Hatton and Vertessy
1990; Thorburn et al. 1993a; McJannet et al.
1999). The instruments used may be operated in
almost any landscape, but only provide estimates of
water uptake by individual plants. Multiple
measurements are required to obtain reliable
estimates of water uptake by vegetation
communities.
• Ventilated chamber – these devices provide
estimates of water uptake by the vegetation they
enclose (Greenwood et al. 1982; Farrington et al.
1989; Clifton et al. 1992; McJannet et al. 1999).
They are most useful for measuring water uptake by
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vegetation in terrestrial grasslands or low
shrublands or by the understorey of forest or
woodland communities.
• Bore hydrograph interpretation - Farrington et al.
(1990) and Salama et al. (1994) describe methods by
which water uptake by phreatophytic vegetation
(plantations and native vegetation communities) may
be estimated from groundwater hydrographs derived
from diurnal logging of groundwater level.
Farrington et al. (1990) estimated evaporation
directly from fluctuations in groundwater level
(after accounting for barometric fluctuations and
aquifer properties). Salama et al. (1994) used a
bore hydrograph separation technique to provide
similar information. The technique is only
applicable to hydrogeological settings in which a
response to direct groundwater uptake can be
detected.
All measurements must be repeated over time to
account for seasonal and year-to-year variability in
water uptake. These techniques measure gross water
uptake and provide no specific indication of
groundwater usage, unless this is clearly defined in
time or long-term plant transpiration exceeds
rainfall. Such measurements would normally be are
used in combination with isotopic techniques
(described below) to estimate the proportion of total
water uptake derived from groundwater.
Isotopic tracers to identify groundwater uptake - the
use of tracers, based on stable isotopes of hydrogen
and oxygen, is emerging as an effective means of
identifying the sources of water in the transpiration
stream of plants. Development of this technique in
Australia was pioneered by Thorburn and his
colleagues (e.g. Thorburn et al. 1993 a,b) in their
work on the extent of stream and groundwater
dependence of vegetation of floodplain forests of the
lower Murray River. It has subsequently been applied
to a range of terrestrial, riparian and wetland
systems with potential groundwater dependency (see
Hatton and Evans 1998).
The technique is based on water from different
sources (groundwater, stream water, soil water)
having different isotopic signatures. Each potential
“pool” of water is sampled and its isotopic signature
determined. Water is extracted from plant tissues
(e.g. small twigs) and the isotopic signature
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compared with that of soil water at different depths
and/or of groundwater or stream water. This
comparison may show a direct correspondence between a
particular pool of water and that taken up by the
plant or it may show a mixing of water from several
sources (after Thorburn et al. 1993b).
These analyses should be repeated over time and may
be combined with measurements of transpiration and/or
soil water fluxes to provide a better understanding
of the extent and proportion of groundwater uptake
(Hatton and Evans 1998). The approach will only work
where the isotopic signature of the various “pools”
of water vary sufficiently to discriminate between
them.
Water balance calculation - Water balance
calculations may be used to quantify groundwater
usage by dependent ecosystems. Calculations are based
on the simple principle that:
Waterin = Waterout + Change in storage.
Accurate calculation of the water balance of an
ecosystem is less straightforward. An outline of the
process and key parameters to be estimated is given
below.
• Define the region – this step determines the scale
of data collection and involves undertaking an
assessment of the key processes operating. The
areal extent of the ecosystem must be determined,
as must the depth and distribution of the relevant
aquifers.
• Rainfall – temporal and spatial distribution of
rainfall must be measured or to provide a measure
of water inputs to the ecosystem.
• Evaporation – evaporation from plant and soil
surfaces should be determined from either direct
measurements (see above; Greenwood 1986) or by
calculation using (e.g.) the Penman-Monteith
equation.
• Surface run-off – the amount of run-off will vary
with the type of landscape and climate. It may be
estimated by catchment modelling or measured by
stream gauging.
• Groundwater recharge – numerous techniques are
available for estimating groundwater recharge.
These are based on interpretation of bore
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hydrograph response, the use of chemical or
radioactive tracers, measurement of soil water
fluxes or groundwater modelling (e.g. Cook and
Herczeg 1998; Walker 1998). Recharge should be
calculated with respect to the various aquifers
present.
• Change in soil water storage – this term is
typically ignored in large-scale long-term water
balance calculations, as under a given vegetation
type and/or land use system, it tends not to vary
greatly from year to year. Measurements of change
in soil water storage may assist in estimation of
evaporation from plants (that part from soil rather
than groundwater) and/or recharge.
• Aquifer throughflow – study area boundaries need to
be well defined to accurately calculate this term.
It is normally estimated using Darcy’s Law and
estimates of the relevant hydrogeological
parameters, viz:
Q = k I A
where, Q = groundwater flux
k = hydraulic conductivity
I = hydraulic gradient
A = cross-sectional area of aquifer
• Groundwater discharge - to rivers, wetlands,
estuaries, the ocean and caves can be estimated
with varying degrees of accuracy by a broad range
of methods including modelling, Darcy’s Law and
stream gauging. Statistical analysis methods are
used with stream hydrograph data to determine the
groundwater derived base flow component.
• Solve water balance – once each of the above
components have been measured, calculated or
assessed they are inserted into the water balance
equation. Calculations should show the component of
the water balance provided by groundwater (it will
generally be an unknown in the equation). Temporal
variation in water balance components over a full
year or a sequence of years to provide an accurate
indication of groundwater usage, particular in
areas where climatic variability is extreme.
Water balance calculations are an excellent means of
investigating hydrologic processes and developing an
understanding of them. However, they are less useful
in estimating groundwater use by dependent
ecosystems. There are significant measurement or
estimation errors in each step of the water balance
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calculation process. If groundwater usage is small
(which is not necessarily the same as having marginal
dependency), this unknown term in the water balance
equation may be swamped by errors in estimating other
terms.
Some terrestrial fauna (e.g. kangaroos in semi-arid
zone) also make consumptive use of groundwater and
should be considered to form part of a groundwater
dependent ecosystem. Although highly dependent on this
consumptive use, the rate of water usage is unlikely to
adequately represent the nature of that dependency. Key
indicators of dependency would be the thresholds of
discharge flux and groundwater level or pressure
required to maintain water availability in the soaks
and pools they water from. Consumptive use by the fauna
is likely to be small relative to direct evaporative
losses.
3.4.3.3 Temporal distribution of groundwater
requirement
The temporal distribution of the natural water regime
and groundwater requirement are important components of
both threshold responses by ecosystems to groundwater
condition and their patterns of consumptive use. It has
three components, as described below.
Timing – timing refers to the seasonality of the
water regime or groundwater requirement. It is
particularly relevant to situations where the water
requirement of the ecosystem is met largely by
groundwater at certain times of year (typically the
dry season) and by other sources (soil water,
rainfall, surface water) for the remainder of the
year.
Changes in the water regime that result in
groundwater not being available at the time of year
when it is most required by the ecosystem may result
in the death of components of that system and/or
successional change to a system that is less
dependent on groundwater.
The importance of timing is illustrated by some
Banksia communities on the Swan Coastal Plain in
Western Australia. In 1991, 100 ha of woodland near
two well fields were severely stressed by two very
hot days that coincided with reduced water levels in
the aquifer. Subsequent investigations showed that
the Banksia woodlands could tolerate a lowering of
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the maximum water table depth by 0.2 m/y up to a
total fall of 1.5 m (Water Authority of Western
Australia 1992).
Duration – the duration of particular elements of a
dependent ecosystem’s water regime or of its pattern
of use may influence key ecological processes.
Certain thresholds of groundwater level (for example)
may need to be maintained for long enough for the
life cycle or breeding phase of certain organisms to
be completed. Changes in water regime that shorten
the period over which this level is maintained may
threaten populations of the species concerned.
Agricultural land use in many areas has produced a
groundwater regime characterised by continued shallow
water tables and the accumulation of salt in the soil
profile and surface waters. Riparian and terrestrial
vegetation may be affected by both the extended
duration of waterlogging and the accumulation of salt
in their root zone. Similar impacts are experienced
by ecosystems within or adjacent to many irrigation
areas (e.g. flood plain forest and woodland
communities along the lower Murray River). Such
ecosystems are an example of inverse groundwater
dependency, where their survival may depend on a
regime where groundwater is less rather than more
available.
Frequency and episodicity – these two terms have
similar meaning. Frequency refers to hydrologic
events that occur or are expected at regular
intervals (e.g. wet season floods in wetlands of
northern Australia). Episodicity refers to events
that occur periodically, but have no particular
pattern, but nevertheless may be important components
of the natural hydrologic regime (e.g. droughts,
flood events in inland semi-arid areas).
Flooding frequency is considered be an important
component of the natural water regime of riparian
ecosystems along the lower Murray River system. Some
trees (e.g. Black Box, E.largiflorens) directly
utilise groundwater and concentrate salt in their
root zone. Regular flooding is required to leach the
salt away and so prevent accumulation to the extent
that vegetation health is threatened and catastrophic
changes in species composition occur (e.g. Jolly et
al. 1993).
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Irregular rainfall and flood events in semi-arid
areas of inland Australia are the source of
groundwater recharge that supplies some groundwater
dependent vegetation communities (e.g. channel water
hole communities, terrestrial fauna dependent on
groundwater soaks). Without such episodes to
periodically replenish the aquifer, the groundwater
dependent elements of the ecosystem could not
survive.
3.5 Water requirement determination
The natural water regime of a groundwater dependent
ecosystem will not necessarily correspond with its
environmental water requirement. The ecosystem may be
able to withstand some degree of change in the water
regime, in terms of flux, level, pressure and/or
quality, before ecological processes are affected.
Determining the environmental water requirement must
therefore consider (Figure 3.1) both the natural water
regime of the ecosystem and the nature of the response
of the ecosystem to change in its water regime. The
latter is the subject of the following section.
Having considered both the natural water regime and the
sensitivity of ecosystems to change, an informed
assessment of the environmental water requirement can
then be made.
The nature of the response of an ecosystem to changes
in its water regime will determine the extent to which
a sustainable environmental water requirement can
differ from the current water regime. Two broad types
of response may be defined (Figure 3.2):
Proportional response – in which there is a
progressive decline in ecological process as the
actual water regime shifts away from the natural
regime. In such cases any change in water regime will
affect ecological processes, although the impact may
only be small initially. Progressive departures from
the natural water regime may result in either a
reduction in the area occupied by the ecosystem (e.g.
a groundwater dependent wetland may contract as water
table levels decline), an increase in the
vulnerability of the ecosystem to further or even
catastrophic change (e.g. as the result of weed
invasion, fire) or smaller populations (e.g. in
aquatic ecosystems with reductions in the size of a
water body).
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Threshold response – in which there may be little
change in ecological function with change in water
regime until a particular threshold is reached. Once
the threshold is exceeded, there would be rapid and
extensive change in ecological process. Water regimes
that are outside the threshold may result in the
ecosystem being greatly simplified or collapsing
entirely.
Aquifer ecosystems may provide an example of this
type of response. Danielopol (1989) and Humphreys
(1999) noted that aquifer ecosystems may be highly
stratified and occupy narrow depth zones. Reductions
in groundwater level (e.g. with abstraction) over a
small range may have only a marginal impact on the
ecosystem. However should the groundwater level drop
to or below the lower limit of the particular species
association, the loss of habitat may result in the
collapse of the entire association.
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Figure 3.2: Illustrations of the broad types of
response function between ecosystem health and water
regime
h e alth y
e c o s ys te m h e alth
Th re s h o ld re s p o ns e
h igh ly
alte re d
Pro p o rtio nal re s p o ns e
wate r re gim e
natu ral
In reality the response of many ecosystems to change in
water regime will be a combination of proportional and
threshold responses.
Ideally, response functions for “ecosystem health” with
change in water regime would be defined and used in
sensitivity analyses to assess the likely impact of
such changes. They would then provide a more objective
basis for determining environmental water requirements.
Response functions could be developed by several means
including:
Benchmarking with similar types of ecosystems –
ecosystem health and water regime would be described
for each example of the particular ecosystem. A
response function would be developed between key
indicators of health and water regime.
Interpretation from historical records – relevant
historical information would be assessed for a
particular ecosystem to detect trends in health and
water regime over time. This would in turn be used to
develop a response function for ecosystem health. The
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types of information that might be used would include
(for example): groundwater and environmental
monitoring, photographic records, species counts,
ecosystem descriptions, presence of dead trees.
Expert opinion - in the absence of empirical
information, expert opinion (alone) may be used to
define the form of the response function and the
level of thresholds in water regime.
Defining ecosystem response to change in water regime
will be difficult for ecosystems (and ecosystem types)
whose ecological processes are poorly understood or
whose water regimes are complex. In such cases there
may even be no “experts” available to offer opinions.
The environmental water requirement would need to be
set arbitrarily, based on the natural or current water
regime.
The environmental water requirement was defined (Figure
1.1) as “the water regime needed to sustain key
ecological values of groundwater dependent ecosystems
at a low level of risk”. Its determination involves a
mix of empirical analysis and subjective assessment.
Even where there exists objective data on the natural
(or current) water regime and some basis for describing
ecosystem health responses to change in water regime,
subjective assessment is likely to be needed to define
“low level of risk”.
The main issue to be considered in assessing the
environmental water requirement is the extent to which
it may differ from the natural water regime. Response
functions, if available, will indicate how ecosystem
health or ecological processes change as the result of
departure from the natural regime (Figure 3.2). The
acceptable level of departure from the natural regime
would be more readily defined for threshold responses.
However, where the response is proportional, value
judgements will be required to set an acceptable level
of decline in ecosystem function.
3.6 Determining the environmental water requirement in
resource and information limited environments
It is expected that environmental water requirement
determinations will be substantially constrained by
resource and/or information availability. In such
circumstances, the full process described in sections
3.2-3.5 and Figure 3.1 might not be appropriate.
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Nevertheless, a reasonable and transparent process for
determining the environmental water requirement is
required.
Less resource intensive assessment processes may also
be appropriate for ecosystems where groundwater
dependency is self-evident and estimation of the
environmental water requirement relatively
straightforward.
Table 3.4 provides an outline of the process for
environmental water requirement assessment that might
be used for three levels of resourcing or complexity.
At low levels of resourcing, the assessment would be
largely based on any published literature and expert
opinion. Moderately resourced investigations and/or
those where the nature of groundwater dependency is
more complex would still largely rely on published
literature and expert opinion. New information would be
sought to specifically identify the groundwater
dependent elements of the ecosystem, to provide a
preliminary indication of their patterns of water use
and to develop a crude response function for change in
ecosystem health with water regime.
Literature review and expert opinion would still be
appropriate in stages for ecosystems with the most
complex groundwater dependency interactions. The key
stages at which new or more detailed information would
be required are similar to those for moderately
resourced investigations, in the identification of
groundwater dependent elements of the ecosystem,
assessment of their patterns of water use and in
developing a response function for change in ecosystem
health with water regime. The major difference is that
this information, particularly in relation to the
patterns of water use of the dependent elements of the
ecosystem, would be obtained using more rigorous
experimental techniques.
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Table 3.4: Guide to level of input for environmental
water requirement assessment given resource and
information availability
Step in Environmental
Water Requirement
determination process
Identification of
groundwater dependency
(3.2)
Dependency analysis
(3.3)
Groundwater
dependent elements
of ecosystem
Low resource &/or
information
availability
Simple groundwater
dependency1
Direct observation,
checklist
Literature review,
expert opinion
Literature review,
Key groundwater
expert opinion
attributes
Literature review,
Type of groundwater
expert opinion
dependency
Assessment of water regime (3.3)
Literature review,
Nature of water
expert opinion
requirement
Literature review,
Source of water
expert opinion
Literature review,
Pattern of water use
benchmarking against
similar ecosystems
Water requirement determination (3.4)
Expert opinion
Ecosystem response
to change
Environmental water
requirement
Current or interpreted
natural water regime
Moderate resource
availability
Moderately complex
groundwater dependency2
High resource
availability
Complex groundwater
dependency3
Direct observation,
checklist, LAI
investigation
Checklist, LAI
investigation, Plant
water relations,
Hydrograph
interpretation
Literature review,
expert opinion, LAI
investigation
Literature review,
expert opinion, LAI
investigation, limited
physiological or
isotope analysis, root
depth sampling
Literature review,
expert opinion
Literature review,
expert opinion
Literature review,
expert opinion
Literature review,
expert opinion
Literature review,
expert opinion
Literature review,
expert opinion
Literature review,
hydrograph
interpretation, base
flow analysis
Literature review,
expert opinion
Literature review,
expert opinion
Literature review,
hydrograph
interpretation, water
use measurements, water
balance studies,
isotope analysis, base
flow analysis
Response function
derived from existing
information –
historical information,
monitoring, other
studies
Water regime
interpreted as
sustaining all key
ecological processes
Low-Moderate
Response function
derived from existing
information –
historical information,
monitoring, other
studies
Water regime expected
to sustain all key
ecological processes
Confidence in
Very low-moderate
Moderate-High
environmental water
requirement
determination
1. Suggested approach to EWR determination for groundwater dependent ecosystems where there is currently
little information available about the water regime and/or nature of dependency and where there are
few resources available to gather new information. May also apply to ecosystems where the
groundwater-ecosystem interactions are readily understood and do not require detailed experimentation
to elicit the nature of these interactions.
2. Suggested approach to EWR determination for groundwater dependent ecosystems where there is existing
information that can be assessed to drawn inferences about groundwater-ecosystem interactions.
Applies also to circumstances where there are resources for limited new investigations of
groundwater-ecosystem interactions.
3. Suggested approach where groundwater–ecosystem interactions are complex and where resources are
available for detailed investigation of those interactions (or where the results of such
investigations are already available).
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4. Environmental water provisions for groundwater dependent
ecosystems
4.1 Introduction
Like most other ecosystems, groundwater dependent
ecosystems exist in environments that have been
modified by human activity. The groundwater that at
least in part sustains these ecosystems has other
values, particularly the provision of water for
agriculture, urban or industrial use. In the past,
environmental uses of groundwater were often
overlooked. While they are increasingly being
recognised, they are inevitably balanced against the
social and economic benefits of non-environmental uses.
Processes are required to define an Environmental Water
Provision (EWP), a water regime that is maintained to
sustain key ecological values of groundwater dependent
ecosystems, but which recognises economic and social,
as well as ecological goals (Water and Rivers
Commission [WRC] 1999; Figure 1.1). The extent to which
the environmental water provision reflects the
environmental water requirement will depend on the
ecological values of groundwater dependent ecosystems
per se and their value in relation to non-environmental
uses of groundwater.
Three approaches have been applied to making
environmental water provisions for groundwater
dependent ecosystems:
No specific provision – the traditional approach to
groundwater resource allocation in many areas has
been to make no specific provision for a water regime
that meets the needs of groundwater dependent
ecosystems. This will not necessarily mean that
environmental water requirements are not met, as
current groundwater allocations may coincidentally
allow an environmentally sustainable water regime.
Alternatively, allocations may not be fully used or
the hydrology of systems may be changed by allocation
and use of groundwater such that ecosystem water
requirements to be met in other ways (e.g. by
enhanced surface drainage from irrigated areas).
However such an approach potentially places
ecological processes in the ecosystems at
considerable risk.
Fixed environmental water provision – blanket
environmental water provisions may be applied such
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that a fixed percentage of average annual groundwater
recharge (for example) is allocated to meet the needs
of dependent ecosystems. In New South Wales, a
blanket EWP of 30% of recharge is being considered
(Department of Land and Water Conservation 2000).
Although potentially leading to a better ecological
outcome than making no specific environmental water
provision, fixed provisions provide no guarantee that
a sustainable water regime will be maintained.
Sophocleous (1997) and Bredehoeft (1997) have
recently reiterated long-standing arguments that
traditional notions of “safe” or “sustainable”
groundwater yields based on maintaining a long-term
balance between annual groundwater abstraction and
annual recharge are unsound. This view of sustainable
yield ignores groundwater discharge and the general
rule that recharge and discharge tend towards
equilibrium in the long-term. Groundwater abstraction
at the average “natural” recharge rate will
ultimately result in the cessation of the “natural”
discharge upon which many groundwater dependent
ecosystems rely. Any regular groundwater abstraction
will ultimately result in reduced discharge (assuming
no change in the recharge characteristics of the
landscape) and may potentially impact on dependent
ecosystems. Recharge, by itself, is considered
irrelevant to sustainable groundwater development and
is not an appropriate benchmark for environmental
water provisions.
Groundwater and/or land use may also result in
contamination, such that the water quality
requirements of dependent ecosystems are not met,
irrespective of the level, pressure or flux regime
maintained.
Environmental water provision based on consideration
of environmental water requirement – there is a
growing body of literature to describe processes by
which environmental water provisions (environmental
flows) for surface water dependent ecosystems can be
determined, based on a thorough consideration of
environmental water requirements. A best practice
framework for the determination of environmental
flows has been proposed for use in Australian studies
(Brizga 1998). Basing environmental water provisions
for groundwater dependent ecosystems on their water
requirements is considered to be the most suitable
approach.
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The extent to which the environmental water
requirement and provision match will determine the
long-term sustainability of dependent ecosystems.
This will be a function of the accuracy with which
the water requirement can be estimated, the condition
and environmental value of the ecosystem and the
extent to which environmental objectives for the
groundwater resource are traded-off against economic
and social objectives.
This section describes a framework for the
determination of environmental water provisions that is
based on an explicit consideration of ecosystem water
requirements and generally follows that developed for
environmental flows for surface water systems.
4.2 Environmental flow provisions
There has been considerable effort in Australia and
internationally to develop and apply methodologies to
determine “environmental flow” requirements for surface
water systems. These methodologies (see review by
Arthington and Zaluki 1998) consider the flow
requirements of a range of geomorphological processes
and components of relevant wetland, riparian,
floodplain, aquatic, estuarine and/or near shore marine
ecosystems. These environmental flow requirements
correspond with the environmental water requirements of
groundwater dependent ecosystems as defined here.
The “environmental flow” concept for surface water
systems per se corresponds with environmental water
provisions concept for groundwater dependent
ecosystems. Environmental flow has been defined as,
“a set of operational rules for water resource
schemes to limit adverse ecological impacts to
acceptable levels”
(Stewardson and Gippel 1997, cited by Brizga 1998)
Like environmental water provisions, they are based on
a consideration of the water required to sustain
geomorphological and ecological process, but also
consider social, economic and (especially for
environmental flows) logistical objectives. Given this,
it is appropriate that processes for determining
environmental water provisions consider those developed
for determination of environmental flows.
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Environmental flow methodologies were reviewed by
Arthington et al. (1998). They outlined two broad
approaches:
Bottom-up approaches – the environmental flow regime
is built up from flows requested for specific
purposes from a starting point of zero flows. Studies
are conducted to determine the flow requirements of
particular geomorphological and ecological processes
and aquatic or other communities
Top-down approaches – the environmental flow regime
is developed by determining the maximum acceptable
departure from natural flow conditions.
Arthington et al. (1998) noted that bottom-up
approaches have traditionally been the most commonly
used approaches, but that top-down approaches are
increasingly finding favour in Australia.
Using the above definitions, bottom-up approaches would
be used to determine the environmental flow
requirement. By definition there is no explicit
recognition of non-environmental values and uses and
the potential need for water provisions to account for
these. Top-down approaches are more likely to deliver
an environmental flow provision, as there is
recognition that the flows provided may depart from
natural conditions.
Arthington et al. (1998) describe a “best practice
framework” for assessing environmental flows (adapted
from Brizga 1998) that incorporates elements of both
bottom-up and top-down approaches. The framework
incorporates:
compilation of existing information about the river
system being investigated;
biophysical investigations of environmental flow
requirements;
participative processes that allow recognition of
human use constraints on water allocation;
peer review, particularly of biophysical
investigations;
socio-economic evaluation;
on-going monitoring and research that feeds back into
reviews of water allocation decisions.
Arthington et al. (1998) envisaged the process being
undertaken by a multi-disciplinary team, comprising
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stakeholders and members with specific technical
expertise.
Within the overall framework, information on
environmental flow requirements could be provided by
one or several bottom-up methodologies. Bottom-up
approaches would also be used to benchmark proposed
water allocations against known impacts on ecological
and geomorphic processes. The framework provides a
useful basis for determining environmental water
provisions for groundwater dependent ecosystems, as is
discussed in the following section.
4.3 Environmental water provisions
The “best practice framework” for assessing
environmental flows that was described by Arthington et
al. (1998) and Brizga (1998) provides a useful basis
for a similar framework for environmental water
provisions. Figure 4.1 outlines such a framework for
groundwater dependent ecosystems. As is shown in Figure
4.1 and described in the following sections, the
process incorporates biophysical investigations,
participatory processes, socio-economic impact
assessment and adaptive management.
It is envisaged that environmental water provisions
would be determined by a multi-disciplinary working
group, comprising the types of stakeholders and
technical specialists listed in Table 4.1. The project
team might be drawn from the following stakeholder and
technical specialist groups:
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Table 4.1: Suggested Environmental Water Provision
Working Group composition
Stakeholders
•
•
•
•
•
•
•
•
Technical Specialists
Groundwater resource managers –
state &/or GMU-wide natural
resource management agencies
State &/or Commonwealth
conservation agencies
Groundwater resource users
Conservation groups
Aboriginal communities
Regional development
organisations
Local government
Catchment management
authorities/boards/committees
•
•
•
•
•
Hydrogeologists
Aquatic and terrestrial
ecologists
Ecohydrologists
Economists
Natural resource planners
•
•
Participative process specialists
GIS Analysts
Elements of the environmental water provision process
that would require stakeholder participation, in
addition to input by technical specialists, are
indicated in Figure 4.1. Stakeholder participation may
also add value at other stages in the processes.
4.3.1 Groundwater basin definition
The basic geographic and hydrogeological unit for
management of groundwater dependent ecosystems would be
a groundwater basin, where the basin defines the three
dimensional extent of specific aquifers and include
recharge and discharge areas. Groundwater basins may be
small or large, depending on the extent of the aquifer.
They may include multiple groundwater management units,
the basic unit for management of groundwater resources.
Ideally environmental water provision assessments would
be carried out on the same geographic basis as
groundwater allocation decisions. This may not always
be possible, as groundwater management units do not
necessarily include discharge and recharge areas.
4.3.2 Compilation of existing knowledge and information
An initial desk top study is required to compile and
review existing information about the groundwater
basin. The types of information sought would relate to:
groundwater and hydrogeological processes
landscapes – geology, geomorphology, topography,
soils
surface water processes and groundwater-surface water
interactions
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climate – seasonal climate (especially balance
between rainfall and evaporation) and longer term
variability (to characterise frequency and severity
of droughts, floods, recharge events etc.)
current and historical land use and management
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Figure 4.1: Framework for assessing environmental
water provisions for groundwater dependent ecosystems
(participatory steps shaded).
Define Groundwater Basin
•
•
Define aquifer(s)
Recharge areas
•
•
Define 3-D extent
Discharge areas
Groundwater processes
Ecosystem descriptions
Compile Existing Information &
R
Surface water processes
Groundwater-surface water
interaction
Maps, GIS layers, remotely sensed
images
Hydrological & hydrogeological
models
Climate
Review Stage 1
•
Familiarisation
with GMU & issues
•
Review financial &
technical resources
available
Environmental Water Requirement
Determination
•
Identify & classify
GDEs
Classify ecosystem
dependency on
groundwater
E osystem
•
•
•
EWR determination
•
•
Groundwater model
Groundwater-surface
water
interaction/processes
Tools to assess change in
water regime with resource
development scenarios
Nature of groundwater
dependency
Strategic Planning
Stakeholder & community input
•
Development proposals
•
Management
vision/objectives
Constraints and
•
•
•
•
Scenario evaluation – groundwater
flow/, level, pressure or quality
Preliminary Environmental Water
Provisions
Expected impacts on GDEs
•
Socio-economic Impact
Assessment
•
•
Market & non-
Social impacts
•
Condition & ecological processes in
GDE’s
Groundwater flow, level, pressure
&/or quality
Nature & extent of
groundwater dependency
Environmental water
requirements
Key knowledge gaps
Establishment of Environmental Water
Provisions
•
Evaluate scenarios
Monitoring
•
Land and water resource use
scenarios for evaluation of
EWR’s and provision impa ts
Supplementary
Investigations
Management Impact Assessment
•
Water resource, environmental
and social objectives
Strategies to
achieve objectives
Knowledge gaps
•
Select preferred
option
Review Process & Adaptive Management
•
•
Evaluate
•
Commission further
monitoring
research
outcomes
Advise on changes in allocations &
descriptions of ecosystems – particularly those that
are appear to be surface and/or groundwater dependent
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conceptual and numerical models of groundwater and/or
surface water processes
significance listings for aboriginal places and
natural and cultural features
current water resource use and allocation.
Information may be compiled from reports and other
publications, databases, libraries of spatial data sets
and remotely sensed images and from anecdotal
information provided by people familiar with the
groundwater basin or ecosystem(s) concerned.
4.3.3 Initial review
The first workshop would have two major objectives; to
familiarise the study team with the groundwater basin
and its specific issues and to provide focus for
activities that support the environmental water
provision assessment.
The corresponding activity in the framework described
by Arthington et al. (1998) was essentially a field
inspection of the river system under investigation. Its
objective would be to ensure team members had a shared
knowledge and understanding of the study area. Such an
approach may be appropriate for relatively small
groundwater basins, but would be impractical for very
large basins (e.g. Great Artesian Basin).
Apart from tours of the basin, familiarisation would be
achieved by reviewing the current status of knowledge
(section 4.3.2). The initial review process would be
used to set the scope and priorities for investigations
of environmental water requirements of groundwater
dependent ecosystems.
4.3.4 Environmental water requirement determination
The first major investigations phase of the process
would seek to determine the environmental water
requirements of groundwater dependent ecosystems within
or reliant on the groundwater basin. The scope of the
environmental water requirement investigations would
depend on resource availability, the status of existing
knowledge and the complexity of ecosystem-groundwater
interactions. Approaches to determining environmental
water requirements are described in section 3.
Determination of environmental water requirements would
ideally be supplemented at this stage by the
development of numerical models of groundwater
processes and (if relevant) groundwater–surface water
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interactions. The models would be constructed and
calibrated at this stage and used later in the process
to assess impacts on the water regime of various
proposed land and water resource use scenarios.
4.3.5 Strategic planning
This stage is one of two key participatory steps in the
environmental water provision process. Its aim is to
introduce the opportunities and limitations for
environmental water provisions posed by nonenvironmental uses and values of groundwater and by
stakeholder and community priorities.
There would be three main inputs to the workshop:
Community and stakeholder aspirations - groundwater
and surface water resource development objectives,
aspirations for dependent ecosystems and issues
related to cultural heritage could pose either
constraints on the allocation of groundwater for
environmental purposes or act as a driver to
encourage such allocations;
Current resource use and development proposals –
existing non-environmental uses of groundwater need
to be considered as do proposals for further resource
development. Groundwater allocation decisions may
require trade-offs between these uses and the
benefits derived from them and environmental uses and
values;
Condition and environmental value of groundwater
dependent ecosystems – the priority given to
environmental values relative to commercial or
utilitarian values should reflect both the condition
and environmental value of dependent ecosystems. The
priority accorded relatively pristine and/or unique
groundwater dependent ecosystems in water allocation
decisions may differ substantially from that accorded
to highly degraded systems and those that are
relatively commonplace (especially if well protected
at other locations).
The workshop would be a facilitated process involving
technical specialists and stakeholder group
representatives. It would:
develop a vision and objectives for the groundwater
management unit. The objectives would have water
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resource development, environmental and socioeconomic dimensions;
identify and allocate priority to the constraints and
drivers to achieving those objectives;
develop broad strategies to achieve objectives for
the groundwater basin and its dependent ecosystems;
specifically identify knowledge gaps that should be
addressed before decisions about environmental water
provisions and groundwater allocation for other uses
are made.
Workshop outcomes would be used to develop a suite of
alternative resource use and environmental water
provision scenarios that would be evaluated to assess
impacts on key ecological processes. These scenarios
would also be subject to socio-economic assessment.
4.3.6 Supplementary investigations
Supplementary investigations may be required to address
the knowledge gaps identified during the strategic
planning activity. The most likely information
requirements would be in relation to developing
response functions (section 3.5) to assess how
ecological health in groundwater dependent ecosystems
declines as the water regime provided departs from the
natural regime.
4.3.7 Management impact assessment
The biophysical impacts of the suite of alternative
resource use and environmental water provision
scenarios would be assessed. Hydrologic modelling would
be used to determine the impact of each scenario on the
water regime that would be experienced by dependent
ecosystems.
Ecological response functions (section 3.5) and/or
expert opinion would be used to assess the impacts of
potential environmental water provisions under each
scenario.
4.3.8 Socio-economic impact assessment
Socio-economic implications of each of the
environmental water provision scenarios would be
considered. The assessment would deal with:
economic benefits and costs of resource use and
environmental water provision scenarios – including
estimates of the market and non-market costs and
benefits of resource use and groundwater dependent
ecosystem management;
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social implications of scenarios, with respect to
cultural heritage issues for indigenous communities,
changed economic environment for resource users and
their communities and outcomes of enhanced
groundwater dependent ecosystem management.
Some information on approaches to economic assessment
of groundwater dependent ecosystem management is
provided in section 7.
4.3.9 Establish environmental water provisions
The second major participatory process would be
undertaken to evaluate the environmental, social and
economic impact assessments. Its principal outputs
would be a preferred option for groundwater allocation
and an environmental water provision. The process would
require inputs from stakeholder groups and technical
specialists.
The workshop would require a facilitated process to
help participants match the biophysical and socioeconomic impacts of alternative groundwater allocation
scenarios against their vision and objectives for the
groundwater basin and its dependent ecological,
economic and social systems. It is suggested that
multi-criteria analysis (MCA) would be a useful tool in
taking stakeholders and technical specialists through a
transparent and semi-objective decision making process.
The approach allows social, economic and environmental
criteria to be included in decision-making processes.
A set of criteria would be developed, based on the
objectives for the groundwater basin. Each of the
alternative environmental water provision scenarios
would then be assessed against these criteria, for
example:
maintenance of ecological function in all groundwater
dependent ecosystems
generation of economic wealth for the community of
the groundwater basin
maintenance of population within groundwater basin
protection of aboriginal places.
The criteria would be ranked for relative importance.
The performance of each scenario in relation to the
criteria would then assessed to provide an overall
evaluation in which scenarios could be ranked against
each other. The environmental water provision would be
based on that specified in the preferred scenario.
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Establishment of the environmental water provision may
be an iterative process, with preliminary environmental
water provision determinations subject to review and
comment by both community and government. Once the
preferred groundwater resource and land use scenario is
adopted and the environmental water provision set,
groundwater managers would establish a system for
groundwater allocation and licensing within the
sustainable yield of the groundwater basin.
4.3.10 Monitoring
Monitoring is required to inform the adaptive system of
groundwater management and, as necessary, to help
develop understanding of ecological processes in
groundwater dependent ecosystems. It would address:
environmental condition of groundwater dependent
ecosystems at particular points in time and the trend
in condition over time. Subject to resources
availability, such monitoring could address key
ecological processes such as recruitment, energy and
nutrient flows and competition and succession. It
would also address any changes in vulnerability to
processes or events that threaten the integrity of
the ecosystem;
water regime, in terms of the groundwater attributes
relevant to ecological processes in the dependent
ecosystems;
allocation and usage of groundwater, which in
combination with monitoring of water regime will
enable comparison between the actual water regime and
that expected under the environmental water
provision;
social and economic monitoring to compare expected
with actual regional development, structural
adjustment and community outcomes.
Environmental and groundwater monitoring would be most
intensive in the early years following establishment of
environmental water provisions (and associated
groundwater allocations). This would be necessary as
part of a process of building up an understanding of
the groundwater system, dependent ecosystems and the
nature of their dependency. The comprehensiveness of
monitoring would also depend on factors such as those
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listed below, each of which would influence the
availability of resources for monitoring:
the size and complexity of the groundwater basin and
groundwater processes;
the value and complexity of groundwater dependent
ecosystems;
the value of human use activities against which
environmental water requirements are balanced.
4.3.11 Review process and adaptive management
Groundwater management systems that make environmental
water provisions for dependent ecosystems must be
adaptive. Periodic reviews that include opportunities
to change groundwater allocations and environmental
water provisions must be built into the management
process.
The review process should be participatory, involving
both technical specialists and stakeholder
representatives. It would:
evaluate the outcomes of environmental monitoring and
any new research relating to ecosystem groundwater
dependency and ecosystem response to changed water
regime;
review the monitoring regime in place, recommending
changes as appropriate;
commission further research to address priority
knowledge gaps and/or issues raised by environmental
monitoring or new resource use developments;
advise government, resource users and other
stakeholders on changes in groundwater allocation
and/or environmental water provisions that may be
considered necessary.
There are circumstances under which changes in
groundwater allocation and/or environmental water
provision may be considered necessary. They would be
highlighted either by on-going monitoring or research
or by new resource use proposals. Examples include
circumstances where:
the environmental condition of dependent ecosystems
has declined to a greater level than expected under
the EWP regime;
monitoring or research has demonstrated that
dependent ecosystems are more resilient to changes in
water regime than originally thought;
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new information has shown that the environmental
significance of the ecosystem is greater than
originally thought and the relative priorities
between environmental and non-environmental uses has
changed;
new resource developments have been proposed that
alter the socio-economic impact of the original
groundwater allocation and EWP regime.
Any major change in the mix of groundwater allocation
between environmental and non-environmental uses would
require stakeholder consultation and review by
community and government.
Infrastructure and associated investments in
groundwater resource developments are unlikely to be
made unless there is a reasonable degree of certainty
about groundwater allocations. While review and
adaptive management processes are essential, they
should recognise the potential social and economic
implications of major changes in water allocations. It
behoves groundwater resource managers where there is
(or will be) large infrastructure investments to ensure
that environmental water requirement studies early in
the planning process are at the level required to
ensure that initial environmental water provisions are
soundly based.
4.4 Implementing environmental water provisions
The effective implementation of environmental water
provisions for groundwater dependent ecosystems
requires coordination and consistent action by the
State agencies with responsibility for groundwater and
natural resource management. This is required in three
domains - policy, technical and operational. Specific
initiatives are discussed below:
Policy – states and territories need to make explicit
policy decisions and statements on how groundwater
dependent ecosystems are to be considered in the
determination of the sustainable yield for an aquifer
and in routine groundwater management and licensing
decision making. Policy decisions are also required
to determine funding arrangements for technical
assessments associated with environmental water
provisions.
Technical - states and territories need to identify
technical knowledge gaps that exist at a groundwater
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management client scale or at the local scale of
individual licence approvals. Depending upon the
confidence required in the final result, the
technical knowledge gaps need to be filled. Fully
allocated or over-allocated groundwater management
units would normally receive the highest priority,
although a broad assessment at a low confidence level
would be undertaken for all groundwater management
units and groundwater basins in each state.
Nonetheless even to assess environmental water
requirements for priority basins/units at a low
confidence level would be a major task for each
state.
Operational - review the sustainable yield values for
all GMUs and groundwater basins to explicitly allow
for groundwater dependent ecosystems. This would be
undertaken either in the framework of the development
of Groundwater Management Plans or on a regular
review time table, perhaps every 5 years.
The framework for assessing environmental water
provisions as depicted in Figure 4.1 should be
applied. While this may not necessarily result in any
change in the sustainable yield, it would provide
greater confidence that the water regime provided for
groundwater dependent ecosystems will meet the
requirements of key ecological processes.
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5. Guidelines for Groundwater Dependent Ecosystem Policy
5.1 Introduction
State and Territory governments need to enact policy
that gives status to groundwater dependent ecosystems
in water allocation decisions and leads to the
establishment of a transparent process for the
determination of environmental water provisions.
Ideally these policies would have a consistent national
framework.
This section provides an overview of national policies
relating to groundwater allocation and the provision of
water for environmental purposes. Since neither deals
explicitly with the provision of water for groundwater
dependent ecosystems, a set of principles have been
proposed.
5.2 National groundwater policy
A national policy on the “Allocation and Use of
Groundwater” (Agricultural and Resource Management
Council of Australia and New Zealand [ARMCANZ] and
Standing Committee on Agriculture and Resources
Management [SCARM] 1996) was developed in response to
an undertaking in the Coalition of Australian
Governments (COAG) Water Reform Framework Agreement.
The policy sets out specific advice to jurisdictions on
appropriate arrangements to ensure that groundwater
management practices are consistent with the intent of
the Framework Agreement. It also identifies a range of
other key reforms directly relevant to the COAG water
reform agenda and provides an important element of the
policy context for groundwater dependent ecosystems.
National policy on allocation and use of groundwater is
based on the need for sustainability. Its first
recommendation is that groundwater management policies
should “employ the principles of ecologically
sustainable development and should be directed at
achieving sustainable use of the resource”. Other
recommendations deal with:
licensing of drillers;
efficient well design and construction;
the need for groundwater management plans based on an
understanding of the resource, its sustainable yield
and level of allocation;
establishment of groundwater information systems that
ensure the collection, maintenance and availability
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of data on bore construction and relevant groundwater
monitoring for at least high yielding bore;
identification and recovery of the full cost of
groundwater management from users;
development of community awareness programs to
reinforce the values of groundwater and its
vulnerability to damage by inappropriate resource or
land use.
The National Framework for Improved Groundwater
Management (ARMCANZ/SCARM 1996) also includes a
specific recommendation that groundwater and surface
water resource management be “better integrated”. While
the focus of this recommendation is on ensuring a
consistent approach to pricing, trading and water
allocation, the issue is clearly relevant to both
groundwater and surface water dependent ecosystems.
In developing groundwater management plans, State
agencies are encouraged to identify environmental water
provisions in accordance with the National Principles
for the Provision of Water for Ecosystems (see section
Table 5.1). Such provisions are to be included as part
of a process by which sustainable yield and existing
allocations and uses of aquifers are assessed.
5.3 Environmental water provisions policy
The Agricultural and Resource Management Council of
Australia and New Zealand (ARMCANZ) and Australian and
New Zealand Environment and Conservation Council
(ANZECC) have prepared a set of 12 principles to give
policy direction on the allocation of water to the
environment (ARMCANZ/ ANZECC 1996; Table 5.1). While
they are meant to apply broadly to the provision of
water for environmental purposes, the wording suggests
a strong focus on surface water dependent ecosystems.
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Table 5.1: Principles for environmental water
allocation for surface water dependent ecosystems
(ARMCANZ/ANZECC 1996)
Goal:
The goal for providing water for the environment is to sustain and where
necessary restore ecological processes and biodiversity of [surface] water
dependent ecosystems.
Principles:
1.
2.
River regulation and consumptive use should be recognised as
potentially impacting on ecological values.
Provision of water for ecosystems should be on the basis of the best
scientific information available on the water regimes necessary to
sustain the ecological values of water dependent ecosystems
3.
Environmental water provisions should be legally recognised.
4.
In systems where there are existing users, provision of water for
ecosystems should go as far as possible to meet the water regime
necessary to sustain the ecological values of aquatic ecosystems
whilst recognising the existing rights and rights of other water
users.
Where environmental water requirements cannot be met due to existing
uses, action (including reallocation) should be taken to meet
environmental needs.
5.
6.
Further allocation of water for any use should only be on the basis
that natural ecological processes and biodiversity are sustained (i.e.
ecological values are sustained).
7. Accountabilities in all aspects of management of environmental water
provisions should be transparent and clearly defined.
8. Environmental water provisions should be responsive to monitoring and
improvements in understanding of environmental water requirements.
9. All water uses should be managed in a manner which recognises
ecological values.
10. Appropriate demand management and water pricing strategies should be
used to assist in sustaining ecological values of water resources.
11. Strategic and applied research to improve understanding of
environmental water requirements is essential.
12. All relevant environmental, social and economic stakeholders will be
involved in water allocation planning and decision-making on
environmental water provisions
5.4 Proposed national principles for water allocation
to groundwater dependent ecosystems
A specific set of national principles for water
allocation to groundwater dependent ecosystems is
proposed (Table 5.2). They essentially restate the
national principles for environmental water allocation
for surface water ecosystems (Table 5.1) in ways that
make their application to groundwater and groundwater
dependent ecosystems explicit.
The principles also draw on those stated in the Western
Australian Environmental Water Provisions Policy
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documents (WRC 1999; 2000) and the New South Wales
Groundwater Dependent Ecosystems Policy (Department of
Land and Water Conservation [DLWC] 2000).
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Table 5.2: Proposed national principles for provision
of groundwater for environmental purposes
Goal:
The goal for providing water for the environment is to sustain and where
necessary restore ecological processes and biodiversity of groundwater
dependent ecosystems.
Principles:
1.
Groundwater abstraction and consumptive use, surface water regulation
and consumptive use, as well as land use practices, should be
recognised as potentially impacting on ecological values of
groundwater dependent ecosystems.
2.
Provision of environmental water should be on the basis of the best
scientific information available on the groundwater regimes, in terms
of flux, level, pressure and/or quality, necessary to sustain the
ecological values of dependent ecosystems. It must include the
identification of key ecological values and processes for groundwater
dependent ecosystems. Where relevant, provision of environmental water
for groundwater dependent ecosystems should integrate groundwater and
surface water requirements. Where information on environmental water
requirements is limited, the precautionary principle should be adopted
in setting interim environmental water provisions, should they be
required.
3.
Environmental groundwater provisions should be legally recognised.
They should form part of estimates of sustainable yield in groundwater
management planning and not generally be tradeable in any water
entitlement market.
4.
Where there are existing users of an aquifer or groundwater basin,
provision of water for dependent ecosystems should go as far as
possible to meet the water regime necessary to sustain their
ecological values whilst recognising the needs of existing water
users.
5.
Where environmental water requirements cannot be met due to existing
uses, action (including reallocation) should be taken to meet
environmental needs. If environmental water requirements cannot be met
without substantially compromising the economic and social benefits of
existing consumptive uses, the environmental risks of not meeting the
ecosystem water requirements and the social and economic costs of
meeting them should be identified and considered in water allocation
planning decision making processes.
6.
Further allocation of water for any use should only be on the basis
that natural ecological processes and biological diversity are
sustained.
7.
In proposing environmental water provisions for groundwater dependent
ecosystems, consideration will be given to environmental changes that
have occurred with historical abstraction, resource management, land
use, water quality impact and/or the capacity for restoration of
altered ecosystems.
8.
Accountabilities in all aspects of management of environmental water
provisions for groundwater dependent ecosystems should be transparent
and clearly defined.
9.
Environmental water provisions should be adaptive, responding to
monitoring, improvements in understanding of environmental water
requirements and/or ecological significance of dependent ecosystems
and to changing demand for consumptive use.
10. All water uses should be managed in a manner that recognises
ecological values.
11. Appropriate demand management and water pricing strategies should be
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used to assist in sustaining ecological values of water resources.
12. Strategic and applied research to improve understanding of
environmental water requirements of groundwater dependent ecosystems
is essential.
13. All relevant environmental, social and economic stakeholders will be
involved in water allocation planning and decision-making on
environmental water provisions for groundwater dependent ecosystems.
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The rationale for most of the principles outlined in
Table 5.2 are explained in the original ARMCANZ/ANZECC
(1996) document. However, the specific rationale and/or
application of each principle to groundwater dependent
ecosystems is described below. New or expanded
principles are given more attention than those that
largely restate principles for surface water dependent
ecosystems.
Principle 1 - recognises the interrelationship of
groundwater, surface water and land use in the
hydrologic cycle of landscapes. Groundwater policy
must not be considered in isolation from either
surface water or land use policy. The principle also
recognises that any consumptive use of groundwater
changes the water regime for dependent ecosystems,
which may, in turn, impact on ecological processes.
Principle 2 – groundwater allocation planning should
be informed by all available scientific information
about the environmental water requirements of
groundwater dependent ecosystems. It should consider
the ecological values (significance, vulnerability)
of the ecosystem and the processes that sustain it.
In the absence of good scientific information, the
precautionary principle (that “measures to prevent
environmental degradation should not be postponed due
to the lack of full scientific certainty when there
is a threat of serious or irreversible damage”)
should be adopted when setting environmental water
provisions.
For many groundwater dependent ecosystems (e.g. base
flow depend systems, unconfined riverine aquifer
systems), distinctions between surface water and
groundwater provisions are arbitrary. Determination
of environmental water requirements and of water
provisions and overall water allocations must be
integrated.
Principle 3 – the COAG Water Reform Framework
Agreement encourages the establishment of a system of
tradeable water entitlements. While operating markets
for such entitlements may be one means of reducing
allocations for consumptive use, environmental water
provisions should not, as a rule, be traded. Periodic
trading of all or part of the annual environmental
water provision allocation may be acceptable provided
there is pressing economic or social need and strong
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evidence that it will not threaten key ecological
processes in the dependent ecosystems.
Principle 4 – ecological values and uses may be only
one of several such values and uses of groundwater in
a particular basins or groundwater management units.
Processes by which groundwater is allocated for
environmental uses must balance the net social,
economic and environmental benefits of these
alternative and often competing uses. However
provision of water for ecosystems should, as far as
possible, meet their water requirements.
Where environmental water provisions cannot be set
without substantially compromising the social and
economic benefits of existing uses, water allocation
planning must be informed by both the ecological
consequences of not meeting environmental water
requirements and the social and economic consequences
of reduced allocation to existing consumptive uses.
Principle 5 - the environmental water requirements of
groundwater dependent ecosystems have a legitimate
stake in groundwater planning. They must not be
ignored simply because a groundwater resource is
already over-allocated for non-environmental uses.
Groundwater planning should include an appropriate
environmental water provision. That provision could
be met through a range of processes, including
reallocation, water conservation and trading.
Principle 6 - allocation of groundwater for nonenvironmental uses, in excess of the existing level
of use should only be made if that water is not
required to meet the environmental water requirement
of dependent ecosystems.
Principle 7 - setting environmental water provisions
will always require balancing environmental, economic
and social objectives for groundwater management. The
priority given to environmental objectives,
specifically the provision of water for dependent
ecosystems, should reflect the condition
(naturalness), value (uniqueness, ecological
significance) and groundwater dependency of the
ecosystem. Environmental water provisions in
groundwater basins with more pristine, unique,
ecologically significant or highly dependent
ecosystems should be given higher priority and more
closely reflect the water requirement than for basins
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with more degraded or better represented ecosystems
or those for which rehabilitation is impractical.
Higher priority for environmental water provisions
may also be given in situations where there is good
opportunity to rehabilitate important ecosystems that
are currently in poor condition.
Principle 8 - any group responsible for managing
environmental water provisions must be accountable to
the Government, the community and other direct
stakeholders. Management of the provision must be
carried out according to transparent protocols that
are directed at meeting stated objectives.
Principle 9 - there will inevitably be uncertainty
associated with environmental water provisions.
Environmental monitoring and periodic review of those
provisions are required to provide maximum
opportunity to detect any environmental decline and
adjust environmental water provisions accordingly.
Principle 10 - it may be possible with some
groundwater dependent ecosystems to integrate
environment water provisions with the allocation of
water for non-environmental uses.
Principle 11 - demand management and water pricing
strategies can be used to improve the efficiency of
consumptive groundwater uses. Application of such
strategies may increase the availability of water for
environmental purposes.
Principle 12 - environmental water requirements of
many groundwater dependent ecosystems are poorly
understood, as are responses of those ecosystems to
changes in water regime. Research is required to
redress this uncertainty and so help to improve the
basis for decision making on environmental water
provisions.
Principle 13 - decisions on water allocations affect
individuals and communities. Resource users and a
wide range of other stakeholder groups have an
interest in groundwater planning and should have
opportunity to participate in planning processes.
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6. Groundwater Management Planning for Dependent Ecosystems
6.1 Introduction
This section provides a brief overview of the
approaches that have been taken by groundwater resource
managers to groundwater dependent ecosystems.
Approaches have been documented for each Australian
state and the Northern Territory. Environmental water
allocation processes in South Africa have also been
documented. This is the only significant international
example where groundwater dependent ecosystems are
considered in groundwater allocation planning.
6.2 New South Wales
The New South Wales government has recently released a
State Groundwater Dependent Ecosystems Policy (DLWC
2000). The document forms part of the State’s
Groundwater Policy framework. It was guided by National
and State Water Reform Agenda and the “National
Principles for Provision of Water for Ecosystems”
(ARMCANZ/ANZECC 1996 – see Table 5.2).
Five management principles for groundwater dependent
ecosystems are enunciated (Table 6.1). They establish
a framework by which groundwater is managed in ways
that ensure, wherever possible, that ecological
processes in dependent ecosystems are maintained or
restored. The principles emphasise the need to
understand the values and ecological processes in
groundwater dependent ecosystems and their response to
change in groundwater regime.
Table 6.1: NSW principles for management of
groundwater dependent ecosystems
1.
Groundwater dependent ecosystems can have important values for
scientists, groundwater managers, groundwater users, ecosystem managers
and the wider community. These values and how threats to them may be
avoided should be identified and action taken to ensure that the
ecosystems are protected.
2.
Groundwater extractions should be managed within the sustainable yield
of aquifer systems, so that the ecological processes and biodiversity
of their dependent ecosystems are maintained and/or restored. This may
involve establishment of threshold levels that are critical for
ecosystem health.
3. Priority should be given to ensuring that sufficient groundwater of
suitable quality is available at all times when it is needed:
• for protecting ecosystems which are known to be, or are most likely
to be, groundwater dependent
• for ecosystems which have an immediate or high degree of threat to
the ecosystem
4.
Where scientific knowledge is lacking, the precautionary principle
should be applied to protect groundwater dependent ecosystems. The
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development of adaptive management systems and research to improve
understanding of these ecosystems is essential to their management.
5. Planning, approval and management of developments and land use
activities should aim to minimise adverse impacts on groundwater
systems by:
• maintaining natural patterns of recharge and not disrupting
groundwater levels that are critical for ecosystems
• not polluting or causing changes in groundwater quality
• rehabilitating degraded groundwater systems where possible
Source: DLWC (2000)
The principles relate environmental water provisions to
sustainable yield in terms of a proportion of long
term average annual recharge. By default 30% of
average recharge is allocated to the environment and
70% for consumptive purposes (the sustainable yield).
The NSW groundwater dependent ecosystem policy provides
for an assessment process to set higher (or lower)
environmental water provisions, based on the value and
sensitivity of the ecosystem.
The flexibility in the process to tailor environmental
water provisions to the needs or values of the
particular ecosystem is appropriate as is the emphasis
on adaptive management systems. However, average
annual recharge may not be appropriate benchmark in
some cases (after Bredehoeft 1997; Sophocleous 1997;
see section 4.1). Environmental water requirements
comprise a water regime of which average annual
recharge is one component (section 3). Use of such a
coarse measure of the water regime may result in key
elements of the groundwater dependency being
overlooked.
NSW groundwater dependent ecosystem policy is to be
implemented through several mechanisms, including
groundwater management plans, groundwater licensing,
environmental planning instruments, education,
monitoring and research. It envisages that the
environmental water provision assessment process will
be participatory and involve broad stakeholder input.
6.3 Northern Territory
It is believed that the relatively low level of
groundwater development, compared to the large size of
the resource in the Northern Territory has resulted in
little impact to date on groundwater dependent
ecosystems. At a local Territory scale, the
sustainable yield assessments undertaken have allowed
for a nominal 50% of the recharge volume to be provided
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for groundwater dependent ecosystems. There is clear
recognition within government of the importance of
groundwater dependent ecosystems, but the active
requirement for determining and environmental water
provision has not yet been made. Nonetheless some major
research projects to determine the environmental water
requirement of groundwater dependent ecosystems are
being undertaken in the Daly River Basin of the
Northern Territory (e.g. Cook et al. 1998).
6.4 Queensland
No general requirement to consider the impact of
groundwater extractions on dependent ecosystems exists
in Queensland and no specific allocations are made.
However there are some special groundwater management
units (e.g. the Sand Islands, Cooloola) that have
restrictions imposed on development because of
environment sensitivity and conservation values.
Although there is some recognition and understanding of
the significance of the river base flow and wetlands
being influenced (if not controlled, in some areas) by
groundwater extractions, there is a strong
understanding of the significance of groundwater
discharge to estuarine and marine ecosystems. As there
are many over-allocated groundwater management units in
Queensland, the potential for dependent ecosystems to
be affected is relatively high.
6.5 South Australia
The South Australian Water Resources Act (1997)
specifically requires that the water requirements
(quantity and quality) of dependent ecosystems are
determined as part of the planning process and, as far
as practical, are provided for. At the core of the
Act, the environment is recognised as a legitimate user
of water that must be provided for.
A licensing regime applies only to parts of the State
where there is strong demand for water and applies
across both surface water and groundwater resources.
The process has three stages, commencing with
development of the water allocation plan. The plan
subsequently receives ministerial consideration and
approval and is then presented to stakeholders through
public consultation processes.
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Water dependent ecosystems are explicitly considered in
the South Australian water allocation planning process.
The governing Act specifies that the environmental
water requirements of water dependent ecosystems must
be considered. Methodologies are applied on a case by
case basis, according to resource availability and the
significance of the ecosystem and the nature of the
water resource.
Detailed investigations to determine the water
requirements of surface water and groundwater dependent
ecosystems of the Chowilla area of the South Australian
Riverland have been completed and studies in the southeast of South Australia have recently commenced.
6.6 Tasmania
The impact of groundwater discharge on surface flows
has been recognised in several of the 14 identified
groundwater management units in Tasmania. There is
currently no licensing of groundwater extraction in
Tasmania. While the impact of groundwater extraction on
groundwater dependent ecosystems is largely unknown, it
is not expected to be great due to the relatively
restricted level of resource development.
6.7 Victoria
The Victorian Water Act (1989) (Section 90)
specifically requires that in the granting of any
groundwater extraction licences any adverse effects on
the environment be considered.
Sustainable yield calculations for the 62 Groundwater
Management Units were undertaken on the basis of
theoretically not allowing any reduction in base flow
to rivers. In practice, the technical data
underpinning many of the sustainable values was limited
and hence the ability to ensure no interaction with
surface waters ranges from being very poor to good.
Groundwater dependent ecosystems other than those
dependent on groundwater base flow have not been even
indirectly considered in the sustainable yield
assessment.
In the regulatory process associated with granting new
licences, the potential impact on surface waters and
vegetation is considered in some cases where large
extraction volumes are proposed. Other groundwater
dependent ecosystems are not considered.
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6.8 Western Australia
The Western Australian government has recently released
its Statewide Policy on Environmental Water Provisions
(Waters and Rivers Commission [WRC] 2000). The policy
builds on a draft policy statement that was released
for public consultation (WRC 1999). It describes the
approach to be followed by the Waters and Rivers
Commission in determining how water will be provided to
protect environmental values during water resource
allocation processes.
The policy was guided by State water and environmental
legislation, the National Strategy on Ecologically
Sustainable Development and the National Principles for
the Provision of Water for Ecosystems. It considered
the environmental water allocation for both surface
water and groundwater dependent systems. The policy
lists 17 “guiding principles” for decisions on
environmental water provisions (Table 6.2).
Implementation of the environmental water provisions
policy has three main components:
State water allocation and planning processes –
environmental water provisions are to be considered
at regional, sub-regional and local area allocation
planning levels;
the determination of EWRs and EWPs – a process is
described that includes identification of key values
and components of water dependent ecosystems,
determination of the environmental water requirement,
an assessment of the social, economic and
environmental trade-offs that may be required when
setting EWPs and review processes;
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Table 6.2: Guiding principles for allocation of water
to the environment in Western Australia
1.
The Commission will undertake water allocation planning and decisionmaking in a way that protects important ecological values and support
ecologically sustainable development consistent with the requirements
of the Rights in Water and Irrigation Act 1914.
2.
In its water resources planning and management processes, the
Commission will aim to ensure that essential natural ecological
processes and the biodiversity of water dependent ecosystems are
maintained. This will require the identification of key ecological
values at regional, sub-regional and management area levels and
recognition of the Environmental Protection Authority’s statutory role
in determining ecological values and objectives.
3.
The water regimes required to maintain the key ecological values at a
low level of risk (i.e. the Ecological Water Requirements) will be
determined on the basis of the best available scientific information.
Where scientific knowledge of ecosystem requirements is limited, and
estimates of interim EWRs and EWPs are required for allocation planning
and licensing processes, the Commission will adopt the “precautionary
principle” as defined in the National Strategy for Ecologically
Sustainable Development (1992).
4.
5.
The Commission will clearly identify the basis for the determination of
EWRs, including where estimates have been based on limited information.
6.
The Commission will continue to encourage, support and conduct research
to improve the state of knowledge on the water regime requirements of
significant ecosystems within Western Australia, and to participate in
national processes to develop and improve approaches to the
determination of EWRs.
7.
The Commission will aim to meet all EWRs when EWPs are proposed. If, in
the view of the Commission, EWRs cannot be met without significantly
compromising the identified economic and social benefits of possible
water allocation strategies, the Commission will ensure that:
•
the risks to ecosystems of not meeting the EWRs are identified ,
together with the social and economic costs of fully meeting the EWRs
• community consultation is undertaken in the development of allocation
scenarios and EWP options
• the proposed allocation strategy are referred to the EPA for
assessment and/or advice under the Environmental Protection Act 1986.
8. In proposing EWPs for developed, partly developed or altered water
resource systems, consideration will be given to the environmental
changes that have occurred due to past flow regulation, water
abstraction, adjacent land uses or water quality effects, as well as
the capacity for restoration of the altered ecosystems.
9.
If, after EWPs have been set, they cannot be met in the short term
because of allocations to existing users, a strategy will be developed
in consultation with users and other stakeholders, to ensure such
provisions are met within the minimum practical timeframe.
10. EWPs will not forma part of any market in tradeable water entitlements.
However, EWPs may be reviewed through a public planning process which
may identify that more or less water is available for consumptive use.
11. Water regimes identified to meet social values (i.e. social water
requirements), will form part of EWPs where they do not unacceptable
impact on significant ecological values.
12. Any mitigation water requirements will be separately identified and are
additional to EWRs. They may form part of EWPs but if this is not
possible, they will normally be met from unallocated water or water
that would otherwise have been available for consumptive use.
13. Further allocations to new or existing users should only occur where
EWPs are being met and monitoring shows that environmental objectives
are being fulfilled. Where EWPs have not been set, allocations to users
will be made on a precautionary basis that minimises ecological risk.
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14. Community involvement and adaptive management are fundamental aspects
of water resources allocation planning and management processes
including the establishment and review of EWPs.
15. Allocation planning and licensing processes will allow for regular
review of allocations and EWPs to consider the implications of improved
knowledge of hydrology, ecology, climate variation and community values
for water management issues.
16. The Commission will require effective management and monitoring to
ensure that EWPs are being met and that environmental values are being
protected.
17. The Commission will require that users are responsible for the
efficient use of their licensed water allocations and for minimising
any ecological damage from their use.
stakeholder participation – to review water resource
management plans and environmental water provisions.
Several other implementation issues were raised in the
policy document, including management of situations
where environmental water provisions would require
reductions in consumptive use, inclusion of water
quality in environmental water provision considerations
and integration of environmental water provision
decisions with other aspects of catchment and waterway
management.
The review noted that under the then existing policy
framework, the provision of water for the environment
was considered at each of three levels:
Regional allocation planning – beneficial uses and
environmental values area assigned to regionally
significant water resources and a preliminary
indication of the quantity of water that may be
diverted provided;
Sub-regional planning – bulk water allocations to
particular consumptive uses are specified, where
cumulative effects of potential developments on the
environment can be assessed and environmental water
provisions (EWPs) incorporated into decision making;
Management area planning – EWPs for a single water
resource are defined and the quantity of water that
can be diverted determined.
The process was considered deficient in several areas,
mostly relating to insufficient procedural and
institutional support for environmental water
provision’s.
The Water and Rivers Commission adopted two guiding
principles:
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water use must be “sustainable” - allocation
decisions must not significantly decrease the rights
of future generations to benefit from water resources
and they must not lead to significant environmental
damage;
water use must be productive – when water is diverted
from the environment it should be used productively
for the benefit of the people of the state and nation
as a whole. The efficient use of water is expected.
The principles stated in the Western Australian
environmental water provisions policy document places
strong emphasis on those environmental objectives.
Water allocation decisions were to be “based on first
ensuring that essential natural ecological processes
and the biodiversity of water-dependent ecosystems are
maintained”. The principles also recognise that
environmental water provisions operate within social
and economic contexts and must consider other resource
management objectives. They call for water allocation
to be a public process and to be adaptive, in that they
are periodically reviewed and that research and
monitoring is undertaken to ensure that environmental
water provisions are meeting their objectives.
6.9 International Approaches
There are few international examples of groundwater
planning that explicitly includes consideration of the
environmental water requirements of groundwater
dependent ecosystems. South Africa appears to be the
only other nation in which specific environmental
groundwater provisions are made.
The South African National Water Act (1998) requires
the determination of water resources required to
maintain environmental values and basic human needs
(called the “Reserve”). The Reserve applies to both
surface water and groundwater resources and is set
aside from any subsequent water allocations.
A range of procedures have been developed to determine
the Reserve:
desk top process – taking only a few days of effort;
intermediate determination – requiring several months
of analysis;
comprehensive determination – potentially requiring
several years of investigation.
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The groundwater component of the intermediate method
for determining the Reserve has been developed (Parsons
1998; Figure 6.1). The comprehensive method is still
under development.
The volume of water available for abstraction is based
on a percentage of average annual groundwater recharge.
Although this volume does not include the Reserve
(which is subtracted from the recharge volume before an
allocation is set), basing allocations on average
recharge means that in the long term there is potential
for conflict with the Reserve (Bredehoeft 1997;
Sophocleous 1997; see section 6.1).
Rules are developed during the Reserve determination
process that allow for protection of groundwater
dependent ecosystems by:
defining an exclusion or protection zone around
sensitive ecosystems and base flow dependent streams
so that there is neither excessive groundwater
drawdown or groundwater contamination from the sea or
saline groundwater or anthropogenic contaminants;
setting maximum draw down levels in aquifers;
ensuring minimum levels of base flow.
Reserve determination appears to explicitly consider
groundwater dependent terrestrial and riparian
vegetation, wetlands and base flow dependent aquatic
ecosystems. The intermediate method makes no mention
of cave and aquifer ecosystems and their water
requirements.
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Figure 6.1: Overview of intermediate method for
determining groundwater component of the South African
“Reserve” (after Parsons 1998)
Delineate boundaries of
significant water resource
Determine homogeneous
response units,
geohydrological region &
geohydrological response
Determine reference
groundwater conditions for
each GHU
Based on quaternary catchments
Classification of each region into “types”, based on role in
hydrological or ecological function
Geohydrological regions become GHU, which are the basic unit
Reference condition represents “natural” physical and
chemical character of groundwater, its depth and variability
in space and time.
Determine current status of
each GHU
Current groundwater condition of GHU described in terms of
degree of use and departure from pristine reference
condition. Status classified according to abstraction,
potential contamination and impacts of abstraction and land
use
Select management class for
each GHU
Management class guides frequency of monitoring and review of
Reserve and limitation on abstraction volume and is based on
current status classification
Quantify the groundwater
allocation for each GHU
Groundwater allocation determined, based on long-term average
annual recharge. Provision for basic human needs and
maintaining base flow requirement are subtracted from average
recharge before allocation set. Level of confidence in
groundwater allocation are stated.
Institute monitoring and
review
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providing for adaptive management
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7. Economics of Protecting Groundwater Dependent Ecosystems
7.1 Introduction
This section examines economic issues relating to the
management of groundwater dependent ecosystems. Its
scope is to identify and quantify the economic impacts
of management practices designed to protect those
ecosystems.
The analysis of economic impacts is limited to a rapid
desktop review of publicly available information.
7.2 Policy background
While ecological issues are the key drivers behind
management decisions to protect groundwater dependent
ecosystems, economic impacts are also important. For
example the Intergovernmental Agreement on the
Environment recommends that ecosystem conservation
measures should:
be cost-effective and not disproportionate to the
environmental problems being addressed
enable those best placed to maximise the benefits
and/or minimise costs
effectively integrate economic and environmental
considerations in decision making processes.
These and other relevant guidelines such as the COAG
Water Reforms define a requirement for an economic
assessment of the impacts of groundwater dependent
ecosystem management.
7.3 Economic impacts of groundwater dependent ecosystem
management
The methods used to manage groundwater dependent
ecosystems will likely vary depending on the specific
problems affecting the resource in question. Generally
speaking management options might include:
limits on the volume of groundwater extractions
conditions relating to the rate of extraction
restrictions of the siting of bores
land use controls
pollution regulations
artificial recharge.
The primary means cited in the literature for ensuring
water availability to groundwater dependent ecosystems
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involves limiting the total volume extracted to the
sustainable yield. In practice this means that if the
current extraction volumes are greater than the
sustainable yield then reductions on usage are
required. Such reductions on consumption (due to an
environmental water provision) would be the major
economic cost of groundwater dependent ecosystem
management. It should be noted that allowance for
environment water provisions would not necessarily be
the only reason for allocations in stressed groundwater
resources to be reduced.
7.3.1 Costs
The costs of reducing groundwater usage depend on the
specific circumstances of the user but could include
costs associated with foregone income from water
dependent economic activities or increased costs
associated with alternative water supplies or improving
water use efficiency. Potential costs of reducing
groundwater usage to allow an environmental water
provision are described below.
No direct impact - many water resources have a mix of
consumer profiles with some consumers using all (or
more than) their water allocation and others that use
less than their allocation. For users with excess
allocation (sleeper licenses) the immediate economic
impact of a restriction on usage could be minimal
depending on the degree to which their usage is less
than their allocation.
Sleeper allocation holders may be disadvantaged if an
environmental water provision regime inhibits them
from trading their excess entitlement.
Alternatively, sleeper licences may become more
valuable as water allocations are reduced, thus
providing windfall profits to licence owners.
Theoretically these windfall profits could be
captured by a management agency and used to
compensate the losers from management changes. A levy
on water trade could be used to achieve this outcome,
although it would be quite complex and require a high
level of intervention by the management agency.
Reduction in water consumption - for some water users
reducing consumption might be the most cost-effective
management action in response to limited availability
of water. For example, an irrigator might plant a
smaller area of crops or a mining company might close
a processing plant. The cost of reductions in water
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consumption can be calculated by reference to the
foregone value of production associated with the
groundwater supply.
A permanent reduction in the allocation available to
an agricultural enterprise that has been developed to
the extent of its full allocation can also result in
stranded investments in irrigation equipment and
supply facilities. The value of the stranded
investment depends on the type and capacity of the
irrigation system and its age and condition.
Moreover, if the water allocation is tied to the
land, then the reduction in allocation will also
affect land values.
Purchase of water from other users - the purchase of
additional water may be the most economic option for
some users, such as irrigators of high value crops or
those with large sunk investments in infrastructure.
Trading is now available in many water resource
systems across Australia. At the margin, the price
of tradeable water reflects the economic value of the
resource and can be used as a proxy of the value of a
small change in environmental entitlement.
The marginal value reflects its value in the highest
valued use rather than the average value across the
water resource.
Thus, for example, the value of
permanently transferred water in the Murray system in
South Australia is approximately $1,000/Ml,
reflecting its value in wine grape production. If
larger quantities of water were available on the
market, the price of water would likely fall as wine
grape requirements are satisfied and water is applied
to less valued crops.
Improved efficiency - improving water supply or
irrigation application and delivery efficiency may be
cost effective where supply systems are leaky or
irrigation practice inefficient. System efficiency is
rarely close to what is technically feasible. The
low cost of water and its widespread availability act
as a disincentive to improved efficiency. However,
the cost of improving efficiency can be large as it
may involve complete replacement of existing supply
or distribution infrastructure. This investment is
only justifiable when the returns from production
exceed costs. In less intensive agricultural
enterprises, the returns from production are low and
operations would not be viable with higher costs
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associated with improving irrigation or supply
efficiency.
When assessing the impacts of adjustment,
consideration has to be given to capital and labour
availability. For example, the adoption of new
irrigation technology generally requires large upfront capital costs which poses a major constraint
for agriculture in particular. Many efficient
technologies are also more labour intensive and this
can be a major constraint on some irrigation
operations.
Alternative water resources - water users may have
access to alternative sources of water. For example,
in the Barossa Valley of South Australia, a reduction
in the availability of groundwater has lead to an
increase in the development of farm dams to capture
overland flows and to the development of a scheme to
transfer water from the Murray basin.
The cost of developing alternative water resources
can be substantial and the viability of such schemes
depends on the returns achieved from water use. In
the case of broadacre agriculture where the returns
per unit of water are relatively low the development
of alternative water resources may not be viable.
Conversely in high value uses such as mining, it may
be viable to utilise very high cost alternatives,
such as desalination or piping of water over large
distances.
Regional impacts - the loss of water availability for
consumptive uses may have wider regional impacts in
addition to the direct impacts on water users. A
reduction in water availability may lead to reduced
agricultural production which in turn will flow on to
the rest of the regional economy. The result may be
lost jobs and foregone income in manufacturing,
transport, and other industries servicing agriculture
or using agricultural outputs.
7.3.2 Benefits
Balancing the costs of management are the environmental
benefits of conserving groundwater dependent
ecosystems. These are somewhat more difficult to
evaluate as they typically involve benefits that cannot
be valued using standard market methods. The key
benefits of groundwater dependent ecosystem management
are the environmental services that arise.
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Environmental economics takes a comprehensive view of
the value of these environment services, using the
concept of total economic value.
Total economic value is composed of a number of
categories of value, direct use, indirect use and nonuse value. The former two are generally referred to
together as “use value”. Each is often further
subdivided into additional categories. By
disaggregating the value of a ecosystem into various
components, the valuation problem generally becomes far
more intelligible and tractable. The three value
categories are described below.
Direct use value - Direct use value derives from
goods that can be extracted from an ecosystem. In the
context of a wetland, for example, extractive use
value could be derived from forage resources or
fishing. Examples of extractive uses of groundwater
dependent ecosystems would appear to be rare. An
exception could be inland fisheries in base flow
dependent river systems.
This category of value is generally the easiest to
measure, since it involves observable quantities of
products whose prices can usually also be measured.
Even when prices cannot be observed (for example,
products harvested for domestic use), there are
generally accepted and reliable ways to estimate the
value of the products (for example, by using the
value of close substitutes or the cost of
collection).
Indirect use value - non-extractive use value derives
from the services which the site provides. For
example, wetlands often filter water, improving water
quality for downstream users, and rivers provide
opportunities for recreation. These services have
value but do not require any good to be harvested.
Although the recreational benefits provided by an
ecosystem are generally considered together as a
single source of value, they are in fact a result of
a number of different services which a site might
provide. The extent of recreational benefits depends
on the nature, quantity, and quality of these
services. Thus, a protected area might provide
trails for hiking, areas for swimming, mooring points
for fishing boats, and so on; and the enjoyment
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derived by visitors from each of these will depend on
such factors as the cleanliness of the water.
Measuring indirect use value is often considerably
more difficult than measuring direct use value. The
‘quantities’ of the service being provided are often
hard to measure. Moreover, many of these services
often do not enter markets so that their ‘price’ is
also extremely difficult to establish.
Non-use value - non-use value derives from the
benefits that a site may provide which do not involve
using the site in any way. In many cases, the most
important non use benefit is existence value - the
value that people derive from the knowledge that the
site exists, even if they never plan to visit it.
For example, people may place a value on the
existence of biological diversity in a particular
(groundwater dependent) ecosystems, even if they have
visited it and probably never will. Loss of species
from that ecosystem may cause people, if they knew
about it, to feel a definite sense of loss.
Economists have suggested a number of motives
underpinning existence values including: bequest
motives relating to the idea of willing a supply of
natural environments to one’s heirs or to future
generations in general; and sympathy for the rights
of the environment.
Another aspect of non-use value is option value.
Option value is the value obtained from maintaining
the option of taking advantage of a site’s use value
at a later date (akin to an insurance policy) and
from the possibility that even though a site appears
unimportant now, information received later might
lead us to re-evaluate it.
Non-use value is the most difficult type of value to
estimate, since in most cases it is not, by
definition, reflected in people’s behaviour and is
thus wholly unobservable. This category of value
also has obvious relevance for the assessment of
groundwater dependent ecosystems, particularly those
such as cave and aquifer ecosystems, which are
relatively obscure.
7.3.3 Discussion
As indicated above the evaluation of the economic
benefits and costs of groundwater dependent ecosystem
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management is resource intensive and requires more
information about the resource and the users than is
generally available to groundwater managers.
Nevertheless it is possible, with a minimum amount of
information, to explore hypothetical scenarios to
identify the possible magnitude of impacts and thus
provide a starting point for discussion about economic
impacts.
7.4 Evaluating the economic costs and benefits of
conserving groundwater dependent ecosystems
Estimates of the costs and benefits of groundwater
dependent ecosystem management on a national scale have
been estimated to illustrate how a high level economic
analysis of these ecosystems might be undertaken.
7.4.1 Benefits of groundwater dependent ecosystem
management
The benefits of conserving groundwater dependent
ecosystems are likely to be in the same order of
magnitude of those found for other water based
ecosystems and other types of natural areas. Table 7.1
sets out willingness to pay (WTP) values from surveys
undertaken for various types of natural areas in
Australia. The data has been converted to an annual
WTP per household and per 10,000 ha of area protected
using the following assumptions:
the total value of preservation is the number of
households in the survey population multiplied by the
average per household once-off WTP payment (in 1999
dollars);
the total value is converted to an annual payment by
assuming that households would contribute to the cost
of preservation over a 30 year period and using a 6 %
discount rate.
Table 7.1 includes two examples of (at least partly)
groundwater dependent ecosystem, the Jandakot wetlands
of Western Australia and the Coorong wetlands of South
Australia.
Table 7.1: Data for estimating the WTP for conserving
natural areas
Study
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Final
Area
Protecte
d
(hectare
s)
Annual unit WTP
(annualized value over 30
years and a 6% discount
rate)
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$/annum/
household in
sample
population
Stone (1991)
Gerrans (1994)
Morrison et al.
(1998)
Bennett et al.
(1997)
Blamey (1998)
Lockwood et al.
(1996)
Lockwood et al.
(1993)
Barmah-Millewa
wetland (Vic)
Jandakot wetlands
(WA)
Macquarie marshes
(NSW)
Coorong (SA)
28 500
2.40
$/annum per
household
to protect
10,000
hectares
0.84
3 800
2.53
6.65
80 000
3.56
0.44
140 000
2.91
0.21
Desert uplands
(QLD)
Bogong High Plains
(Vic)
East Gippsland
(Vic)
688 000
5.52
0.08
50 000
3.00
0.60
100 000
4.22
0.42
Households are willing to pay between $2.00 to $5.00
p.a. to preserve natural areas. On a unit per hectare
basis the WTP values range from approximately $0.10 to
$7.00 per 10 000 ha protected.
The data set out above can be used as a guide to the
likely value of groundwater dependent ecosystems and
hence the economic viability of preserving groundwater
dependent ecosystems. To do this the area of
groundwater dependent ecosystems in Australia has been
estimated and the costs of preservation and then
compared the likely cost per household against the
threshold values suggested in Table 7.1.
It has been assumed that the scope of the analysis is
limited to totally and highly dependent groundwater
dependent ecosystems. The area of these types of
ecosystem has been calculated using two step process
involving:
measuring the area delineated as containing totally
and highly dependent groundwater dependent ecosystems
from the wetland ecosystem maps in Hatton and Evans
(1998).
estimating the actual area of groundwater dependent
ecosystems using satellite imagery greenness
persistence index data for arid areas of Australia.
The results are set out in Table 7.2.
Table 7.2: Data for estimating the area of totally and
highly dependent groundwater dependent ecosystems
Item
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Area of Australian
containing wetland
ecosystems which are
entirely or highly
dependent on
groundwater.
Proportion of arid zone
Landsat scene with
extremely or very high
greenness persistence
index.
2 261 316 km2
Hatton and Evans (1998)
0.7%
1 582 000 ha
Morton et al. (1997)
7.4.2 Costs of groundwater dependent ecosystem
management
It is reasonable to assume that the preservation of
groundwater dependent ecosystems will require some type
of management intervention. This could take the form
of:
controls on land use in aquifer recharge areas;
groundwater pollution prevention strategies;
controls on groundwater bore location; or
restrictions on groundwater use.
For the purpose of the analysis it has been assumed
that the management intervention will involve
restrictions on groundwater use. The cost to
groundwater users is calculated assuming that
restriction involves a percentage reduction in current
use for all groundwater consumption and that the
economic cost is estimated in terms of value-added per
ML of water consumed for each of the major categories
of groundwater user (e.g. domestic and stock,
irrigation and industrial/commercial).
The data used in the estimation of costs is as follows:
total groundwater use has been sourced from the 1985
Review of Australia Water Resources and Water Use
which presents data from the year 1983-84;
it is assumed that groundwater use has increased at a
rate of 1 % p.a. since 1983-84;
the proportion of groundwater consumption by
different use categories is as for 1983-84 e.g. 58%
irrigation, 32% domestic and stock and 10%
industrial/urban;
within the domestic and stock category 78% is used
for stock watering and 22% for domestic use and in
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the industrial/urban category 59% of water use is
domestic and 41% is industrial/commercial;
value added per ML of $300 p.a. for irrigation, based
on average industry values derived from data sourced
from ATSE (1999);
for industrial use the value added per ML is $80,000,
given this large opportunity cost it is likely that
these consumers would employ alternative water supply
options rather than forgo production opportunities,
accordingly for this category an average cost based
on desalination of $1,500/ML p.a. is used;
for urban consumers the WTP for water supply is
assumed to be the average water supply revenue per ML
of water supplied which was approximately $1,200/ML
p.a. in 1998/99;
for the stock component of domestic and stock a value
of $150/ML is used and for the domestic is has been
assumed that the same WTP as used for urban consumers
applies e.g. $1,200/ML.
The value used in calculating costs to water consumers
are summarised in Table 7.3.
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Table 7.3: Data for estimating the costs of
restrictions on groundwater use
Category
Quantity (GL)
Value ($/ML/annum)
1522
300
Irrigation
Domestic &
Stock
Domestic
185
1 200
Stock
655
150
Urban/industria
l
Domestic
154
1 200
Industrial
108
1 500
7.4.3 Benefit cost assessment
An estimate of the benefits and costs of conserving
groundwater dependent ecosystems in their current
condition has been calculated using the data and
assumptions described above. The analysis examines
community economic benefits and the economic costs
imposed on groundwater consumers from restrictions on
consumption.
The results of the analysis are set out in Table 7.4.
The level of restriction required to conserve
groundwater dependent ecosystems is unknown, but for
this analysis it is assumed that the required
restriction is at least 10%. Impacts have been modelled
in the range 0% to 20% of the current level of
consumption. Costs are the foregone value added or
consumer surplus from water consumption arising from a
specified level of restriction on water use. The
required level of community benefits that would just
offset the cost to consumers is calculated for each
restriction level.
Table 7.4:
Benefit costs analysis results
Restriction on
groundwater use
to conserve GDEs in
current condition
(% of current
diversion)
Cost to
groundwater
consumers
($m/annum)
0
0
Required Community WTP to
conserve GDEs in
current condition
($/household/an
num)
0
$/
household/annum
to protect
10,000
hectares)
0
5
56
8
0.05
10
112
16
0.10
15
169
24
0.15
20
225
32
0.20
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At the assumed 10% base case level of restriction the
conservation of groundwater dependent ecosystems would
impose a cost of $112 million on consumers. If these
costs are to be just balanced by benefits to the
community (eg the cost benefit ratio equals one) then
the community benefits must be at least $16 per
household.
The studies summarised Table 7.1 suggest households are
willing to pay between $2.00 to $5.00 per annum to
preserve natural areas ranging in size from a couple of
thousand hectares up to 600,000 hectares. A value of
$16 per household to preserve all groundwater dependent
ecosystems is at least 2 to 3 times what households
have indicated they are willing to pay for these other
area, albeit the other areas are single sites with
unique and identifiable conservation characteristics.
In contrast groundwater dependent ecosystems encompass
a wide range of ecosystem types with a range of
conservation values and dispersed over a many
locations.
The required willingness to pay is approximately $0.10
per 10,000 ha of groundwater dependent ecosystem
protected. This value is at the lower end of the per
hectare WTP estimates set out in Table 7.1. This would
be consistent with the expected downward sloping (in
terms of hectares protected) demand curve for natural
area conservation. Accordingly on an area basis the
preservation of groundwater dependent ecosystems would
seem to be economic assuming 10% base case level of
restrictions.
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8. Conclusions
Groundwater dependent ecosystems:
The groundwater dependent ecosystems of Australia
represent a diverse, yet distinct component of the
nation’s biological diversity. Six types of ecosystem
have been identified and described:
terrestrial vegetation
wetlands
estuarine and near shore marine systems
river base flow systems
cave and aquifer ecosystems
terrestrial fauna
The common thread that links these ecosystems is the
dependency of at least some ecological processes on
groundwater. The identification of ecosystems as
groundwater dependent is not generally at an advanced
stage. Many ecosystems are poorly understood, despite
their often extremely high conservation value.
Groundwater and dependent ecosystems in many parts of
Australia are facing increasing pressure from
consumptive uses and land use factors. Key threatening
processes include:
water resource development
agricultural land use
activation of acid sulphate soils
urban and commercial development
mining
plantation forestry
The water regimes and water quality experienced by
groundwater dependent ecosystems are changing in ways
that pose (largely) unknown, but potentially
significant threats to their ecological function.
A system of classification has been developed for
groundwater dependent ecosystems. Importance of the
ecosystem is expressed in terms of the conservation
value of the system, its vulnerability to potential
threats and the likelihood of threats being realised.
Environmental water requirements of groundwater
dependent ecosystems:
The concept of making provision of water for
environmental purposes is not a new one. Environmental
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flow allocations to sustain ecological and geomorphic
processes in surface water systems have been considered
in Australia for a decade or more. By contrast there is
limited experience in the provision of water to meet
the needs of such processes in groundwater dependent
ecosystems.
Environmental water requirements may be derived from an
understanding of four key factors:
the nature of ecosystems’ dependency on groundwater
the water requirements of the ecosystem;
the groundwater regime that will satisfy the water
requirements of the ecosystem;
the impacts of change in groundwater regime on
ecological processes.
A conceptual framework for the process by which these
information requirements may be met and, in effect, the
environmental water requirements of groundwater
dependent ecosystems determined has been outlined. The
framework can be applied in a range of operating
environments, from those that are tightly constrained
by information and resource availability to those that
are not.
Environmental water provisions for groundwater
dependent ecosystems:
The management of groundwater, like other forms of
natural resource management is to operate according to
the principles of Ecologically Sustainable Development.
To do so, groundwater resources must be managed in ways
that conserve biological diversity. This can only be
achieved if some allocation of groundwater is provided
to meet the needs of dependent ecosystems
Implementation of environmental water provisions
depends on there being:
commitment by State groundwater and natural resource
management agencies to make such provisions and to
adequately resource investigations that support
environmental water provision determinations;
information with which to assess the water regime
required to meet the needs of groundwater dependent
ecosystems;
a adaptive system of managing groundwater resources,
based on comprehensive environmental and resource use
monitoring, that allows response to unexpected and
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adverse trends in environmental condition as the
result of groundwater resource use.
A framework has been proposed for the determination of
environmental water provisions that is based on an
explicit consideration of ecosystem water requirements.
Its key elements include:
determination of the environmental water requirement;
stakeholder participation to identify economic,
social and environmental objectives for the
groundwater resource;
balancing a consideration of the condition and value
of the groundwater dependent ecosystem and the
environmental, economic and social impacts of
providing that water regime needed to meet the
environmental water requirement with consideration of
the environmental, economic and social impacts of
alternative water allocation scenarios
a system of monitoring, review and adaptive
management.
Economics of managing groundwater dependent ecosystems:
An estimate of the economics of conserving groundwater
dependent ecosystems on a national level has been
undertaken using a rapid evaluation approach. This
approach provides an approximate and very broad
indication of the economic viability of conservation.
Based on some broad assumptions, the costs of
groundwater dependent ecosystem management were
estimated to be in the range $112 - $225 million per
annum. This estimate is based on the potential cost of
reducing water use sufficiently to make environmental
water provisions for groundwater dependent ecosystems
at a national level. The cost per household is at least
2 to 3 times what households have indicated they are
willing to pay for protecting other types of natural
areas. However, on a per hectare basis, these costs are
roughly equivalent with the amounts consumers are
willing to pay for the protection of other similar
natural areas.
Groundwater dependent ecosystem policy:
The Coalition of Australian Governments Water Reform
Framework Agreement provides a sound policy context for
the sustainable use of groundwater resources through
the provision of water to meet the environmental needs
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of dependent ecosystem. Under this framework, a set of
principles for the provision of water for the
environment have been developed. However, the language
used is most applicable to surface water dependent
systems. These principles have been therefore been
reworded to reflect the specific issues associated with
groundwater dependent ecosystems.
Groundwater planning:
There is wide variability between the groundwater
planning processes used in each of the Australian
states and territories. This is particularly true in
the provision of water for groundwater dependent
ecosystems. There is a strong emphasis on environmental
water provisions in groundwater allocation planning in
Western Australia, New South Wales and South Australia.
Attention to the water requirements of these ecosystems
is modest in other states and territories. The
potential implications of this are greater in
Queensland and Victoria, where many groundwater
management units are over-allocated, despite the
current lack of explicit recognition of environmental
water provision.
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9. Recommendations
Recommendations arising from this study fall into two
areas, the need to fill knowledge gaps and the need for
groundwater allocation planning processes in all states
and territories to adequately consider the needs of
groundwater dependent ecosystems.
Knowledge gaps:
It is recommended that Commonwealth and State
governments make further investment in research and
investigations to:
identify groundwater dependent ecosystems;
determine the conservation status of groundwater
dependent ecosystems, particularly those ecosystems
most threatened by groundwater resource development
and land use factors;
develop a priority ranking of groundwater dependent
ecosystems, based on conservation status and
vulnerability to and risk of changed water regime;
understand the response of key groundwater dependent
ecosystems to changes in their water regime.
Groundwater allocation planning processes:
It is recommended that State and Territory groundwater
resource management agencies incorporate the following
in their allocation planning processes:
specific provision of water to meet the environmental
requirements of groundwater dependent ecosystems;
integrated consideration of the environmental
requirements of surface water and groundwater
dependent ecosystems where groundwater and surface
waters interact;
processes to determine the environmental requirements
of groundwater dependent ecosystems;
processes that make environmental provisions based on
an understanding of the water regime required to
sustain ecological processes in dependent ecosystems;
processes that make environmental provisions that are
also transparent, participative and based on a
thorough assessment of the social, economic and
environmental implications of those provisions.
It is further recommended that a set of national
principles for water allocation for groundwater
dependent ecosystems be prepared and adopted by State
and Territory governments.
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11. Glossary
Several key terms that are used in this report have
been defined below to ensure a common understanding of
their meaning. Definitions are based on those given
ARMCANZ and ANZECC (1996) and Water and Rivers
Commission (1999).
Environment – refers to the natural components of
ecosystems – flora and fauna – and the natural
ecological processes that take place between
individual plants and animals, their surroundings and
each other. The maintenance of species biodiversity,
community structure and functioning and natural
ecological processes are important elements (and
indicators) of the maintenance of overall
environmental integrity.
Groundwater dependent ecosystems – those parts of the
environment, the species composition and natural
ecological processes of which are determined by the
permanent or temporary presence or influence of
groundwater.
Ecological values – natural ecological processes
occurring within groundwater dependent ecosystems and
the biodiversity of these systems.
Environmental water requirements – descriptions of
the groundwater regimes needed to sustain the
ecological values of dependent ecosystems at a low
level of risk. These descriptions are developed
through the application of scientific methods and
techniques and/or local knowledge and long-term
observation.
Environmental water provisions –the environmental
water regimes that are to be maintained. They are set
by water allocation decisions that may involve
compromise between ecological, social and economic
goals.
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12. Acknowledgments
The Sinclair Knight Merz project team would like to
acknowledge the contributions of our co-worker, Dr Tom
Hatton of CSIRO Land and Water to the project and this
report.
The report was reviewed by Dr Ray Froend of Edith Cowan
University, Dr Andy Spate of the NSW National Parks and
Wildlife Service and Dr Chris Gippel and Kerry Olsson
for Environment Australia.
Environment Australia funded the consultancy under
which this report was written. Sinclair Knight Merz
would like to thank Environment Australia Gayle Stewart
of Environment Australia and Dr Chris Gippel, the
National River Health Program Coordinator, for their
interest in and support for the project.
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